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	$173.82	12.827%	$196.1159	$196.12	$196.10	$196.10
Purchase #2	$136.59	12.148%	$153.183	$153.18	$153.20	$153.20
Purchase #3	$62.68	7.509%	$67.3866	$67.39	$67.40	$67.40
Purchase #4	$108.75	7.250%	$116.6344	$116.63	$116.65	$116.60
Purchase #5	$164.94	6.533%	$175.7155	$175.72	$175.70	$175.70
Purchase #6	$32.76	7.348%	$35.1672	$35.17	$35.15	$35.20
Purchase #7	$173.58	12.140%	$194.6526	$194.65	$194.65	$194.70
7 purchase totals =	$853.12		$938.8552	$938.86	$938.85	$938.90