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	$237.34	13.808%	$270.1119	$270.11	$270.10	$270.10
Purchase #2	$66.92	10.214%	$73.7552	$73.76	$73.75	$73.80
Purchase #3	$68.87	4.263%	$71.8059	$71.81	$71.80	$71.80
Purchase #4	$97.36	11.331%	$108.3919	$108.39	$108.40	$108.40
Purchase #5	$181.72	8.125%	$196.4848	$196.48	$196.50	$196.50
Purchase #6	$240.50	5.540%	$253.8237	$253.82	$253.80	$253.80
Purchase #7	$67.31	4.282%	$70.1922	$70.19	$70.20	$70.20
7 purchase totals =	$960.02		$1,044.5656	$1,044.56	$1,044.55	$1,044.60