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	$45.74	13.539%	$51.9327	$51.93	$51.95	$51.90
Purchase #2	$198.34	5.825%	$209.8933	$209.89	$209.90	$209.90
Purchase #3	$233.37	8.689%	$253.6475	$253.65	$253.65	$253.60
Purchase #4	$110.29	7.543%	$118.6092	$118.61	$118.60	$118.60
Purchase #5	$145.89	3.463%	$150.9422	$150.94	$150.95	$150.90
Purchase #6	$223.79	8.729%	$243.3246	$243.32	$243.30	$243.30
Purchase #7	$22.39	13.344%	$25.3777	$25.38	$25.40	$25.40
7 purchase totals =	$979.81		$1,053.7272	$1,053.72	$1,053.75	$1,053.60