Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$101.42	10.515%	$112.0843	$112.08	$112.10	$112.10
Purchase #2	$243.40	8.803%	$264.8265	$264.83	$264.85	$264.80
Purchase #3	$151.72	7.836%	$163.6088	$163.61	$163.60	$163.60
Purchase #4	$127.57	12.465%	$143.4716	$143.47	$143.45	$143.50
Purchase #5	$181.45	13.594%	$206.1163	$206.12	$206.10	$206.10
Purchase #6	$69.89	12.581%	$78.6829	$78.68	$78.70	$78.70
Purchase #7	$199.41	6.114%	$211.6019	$211.60	$211.60	$211.60
7 purchase totals =	$1,074.86		$1,180.3923	$1,180.39	$1,180.40	$1,180.40