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	$203.60	3.862%	$211.463	$211.46	$211.45	$211.50
Purchase #2	$46.33	9.841%	$50.8893	$50.89	$50.90	$50.90
Purchase #3	$222.89	8.854%	$242.6247	$242.62	$242.60	$242.60
Purchase #4	$89.69	3.177%	$92.5395	$92.54	$92.55	$92.50
Purchase #5	$184.56	5.502%	$194.7145	$194.71	$194.70	$194.70
Purchase #6	$247.48	9.529%	$271.0624	$271.06	$271.05	$271.10
Purchase #7	$152.38	8.384%	$165.1555	$165.16	$165.15	$165.20
7 purchase totals =	$1,146.93		$1,228.4489	$1,228.44	$1,228.40	$1,228.50