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	$10.41	10.496%	$11.5026	$11.50	$11.50	$11.50
Purchase #2	$106.37	8.442%	$115.3498	$115.35	$115.35	$115.30
Purchase #3	$223.59	13.708%	$254.2397	$254.24	$254.25	$254.20
Purchase #4	$196.98	12.730%	$222.0556	$222.06	$222.05	$222.10
Purchase #5	$167.26	11.145%	$185.9011	$185.90	$185.90	$185.90
Purchase #6	$141.43	7.127%	$151.5097	$151.51	$151.50	$151.50
Purchase #7	$216.74	13.414%	$245.8135	$245.81	$245.80	$245.80
7 purchase totals =	$1,062.78		$1,186.3720	$1,186.37	$1,186.35	$1,186.30