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	$165.78	3.283%	$171.2226	$171.22	$171.20	$171.20
Purchase #2	$57.69	3.560%	$59.7438	$59.74	$59.75	$59.70
Purchase #3	$95.96	3.872%	$99.6756	$99.68	$99.70	$99.70
Purchase #4	$61.44	3.528%	$63.6076	$63.61	$63.60	$63.60
Purchase #5	$235.28	13.523%	$267.0969	$267.10	$267.10	$267.10
Purchase #6	$242.26	9.178%	$264.4946	$264.49	$264.50	$264.50
Purchase #7	$170.72	11.577%	$190.4843	$190.48	$190.50	$190.50
7 purchase totals =	$1,029.13		$1,116.3254	$1,116.32	$1,116.35	$1,116.30