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	$108.40	7.510%	$116.5408	$116.54	$116.55	$116.50
Purchase #2	$148.73	3.164%	$153.4358	$153.44	$153.45	$153.40
Purchase #3	$45.52	6.185%	$48.3354	$48.34	$48.35	$48.30
Purchase #4	$113.51	6.179%	$120.5238	$120.52	$120.50	$120.50
Purchase #5	$212.71	10.190%	$234.3851	$234.39	$234.40	$234.40
Purchase #6	$186.27	5.302%	$196.146	$196.15	$196.15	$196.10
Purchase #7	$8.56	11.502%	$9.5446	$9.54	$9.55	$9.50
7 purchase totals =	$823.70		$878.9115	$878.92	$878.95	$878.70