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	$152.57	9.567%	$167.1664	$167.17	$167.15	$167.20
Purchase #2	$245.89	10.632%	$272.033	$272.03	$272.05	$272.00
Purchase #3	$221.44	8.662%	$240.6211	$240.62	$240.60	$240.60
Purchase #4	$30.42	4.478%	$31.7822	$31.78	$31.80	$31.80
Purchase #5	$47.49	12.307%	$53.3346	$53.33	$53.35	$53.30
Purchase #6	$247.63	6.499%	$263.7235	$263.72	$263.70	$263.70
Purchase #7	$69.64	3.140%	$71.8267	$71.83	$71.85	$71.80
7 purchase totals =	$1,015.08		$1,100.4875	$1,100.48	$1,100.50	$1,100.40