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	$214.82	7.742%	$231.4514	$231.45	$231.45	$231.50
Purchase #2	$52.42	6.165%	$55.6517	$55.65	$55.65	$55.70
Purchase #3	$248.86	8.290%	$269.4905	$269.49	$269.50	$269.50
Purchase #4	$73.77	5.813%	$78.0583	$78.06	$78.05	$78.10
Purchase #5	$142.62	5.362%	$150.2673	$150.27	$150.25	$150.30
Purchase #6	$195.82	6.713%	$208.9654	$208.97	$208.95	$209.00
Purchase #7	$56.98	3.360%	$58.8945	$58.89	$58.90	$58.90
7 purchase totals =	$985.29		$1,052.7791	$1,052.78	$1,052.75	$1,053.00