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	$140.98	12.275%	$158.2853	$158.29	$158.30	$158.30
Purchase #2	$142.27	12.222%	$159.6582	$159.66	$159.65	$159.70
Purchase #3	$187.77	4.178%	$195.615	$195.62	$195.60	$195.60
Purchase #4	$143.27	8.632%	$155.6371	$155.64	$155.65	$155.60
Purchase #5	$137.83	4.687%	$144.2901	$144.29	$144.30	$144.30
Purchase #6	$249.27	6.432%	$265.303	$265.30	$265.30	$265.30
Purchase #7	$145.86	7.287%	$156.4888	$156.49	$156.50	$156.50
7 purchase totals =	$1,147.25		$1,235.2775	$1,235.29	$1,235.30	$1,235.30