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	$158.48	10.622%	$175.3137	$175.31	$175.30	$175.30
Purchase #2	$199.88	11.374%	$222.6144	$222.61	$222.60	$222.60
Purchase #3	$223.33	11.709%	$249.4797	$249.48	$249.50	$249.50
Purchase #4	$246.47	5.370%	$259.7054	$259.71	$259.70	$259.70
Purchase #5	$158.59	5.419%	$167.184	$167.18	$167.20	$167.20
Purchase #6	$77.99	5.315%	$82.1352	$82.14	$82.15	$82.10
Purchase #7	$134.64	10.642%	$148.9684	$148.97	$148.95	$149.00
7 purchase totals =	$1,199.38		$1,305.4008	$1,305.40	$1,305.40	$1,305.40