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	$40.33	10.364%	$44.5098	$44.51	$44.50	$44.50
Purchase #2	$249.63	12.741%	$281.4354	$281.44	$281.45	$281.40
Purchase #3	$84.91	5.163%	$89.2939	$89.29	$89.30	$89.30
Purchase #4	$172.33	6.818%	$184.0795	$184.08	$184.10	$184.10
Purchase #5	$61.75	3.654%	$64.0063	$64.01	$64.00	$64.00
Purchase #6	$184.65	5.788%	$195.3375	$195.34	$195.35	$195.30
Purchase #7	$197.66	12.258%	$221.8892	$221.89	$221.90	$221.90
7 purchase totals =	$991.26		$1,080.5516	$1,080.56	$1,080.60	$1,080.50