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	$140.87	7.559%	$151.5184	$151.52	$151.50	$151.50
Purchase #2	$96.61	10.658%	$106.9067	$106.91	$106.90	$106.90
Purchase #3	$209.45	4.782%	$219.4659	$219.47	$219.45	$219.50
Purchase #4	$250.56	11.624%	$279.6851	$279.69	$279.70	$279.70
Purchase #5	$45.69	4.353%	$47.6789	$47.68	$47.70	$47.70
Purchase #6	$237.60	11.492%	$264.905	$264.91	$264.90	$264.90
Purchase #7	$190.49	4.414%	$198.8982	$198.90	$198.90	$198.90
7 purchase totals =	$1,171.27		$1,269.0582	$1,269.08	$1,269.05	$1,269.10