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	$219.63	4.516%	$229.5485	$229.55	$229.55	$229.50
Purchase #2	$178.64	5.668%	$188.7653	$188.77	$188.75	$188.80
Purchase #3	$154.35	3.263%	$159.3864	$159.39	$159.40	$159.40
Purchase #4	$227.59	5.632%	$240.4079	$240.41	$240.40	$240.40
Purchase #5	$63.27	13.126%	$71.5748	$71.57	$71.55	$71.60
Purchase #6	$97.81	13.722%	$111.2315	$111.23	$111.25	$111.20
Purchase #7	$36.65	5.465%	$38.6529	$38.65	$38.65	$38.70
7 purchase totals =	$977.94		$1,039.5673	$1,039.57	$1,039.55	$1,039.60