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	$222.90	5.366%	$234.8608	$234.86	$234.85	$234.90
Purchase #2	$149.37	8.559%	$162.1546	$162.15	$162.15	$162.20
Purchase #3	$151.40	13.229%	$171.4287	$171.43	$171.45	$171.40
Purchase #4	$78.43	3.378%	$81.0794	$81.08	$81.10	$81.10
Purchase #5	$50.49	7.599%	$54.3267	$54.33	$54.35	$54.30
Purchase #6	$237.70	11.369%	$264.7241	$264.72	$264.70	$264.70
Purchase #7	$99.90	6.395%	$106.2886	$106.29	$106.30	$106.30
7 purchase totals =	$990.19		$1,074.8629	$1,074.86	$1,074.90	$1,074.90