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	$119.33	6.745%	$127.3788	$127.38	$127.40	$127.40
Purchase #2	$82.32	11.288%	$91.6123	$91.61	$91.60	$91.60
Purchase #3	$159.84	13.133%	$180.8318	$180.83	$180.85	$180.80
Purchase #4	$230.68	11.764%	$257.8172	$257.82	$257.80	$257.80
Purchase #5	$21.35	4.674%	$22.3479	$22.35	$22.35	$22.30
Purchase #6	$64.59	4.498%	$67.4953	$67.50	$67.50	$67.50
Purchase #7	$148.59	13.542%	$168.7121	$168.71	$168.70	$168.70
7 purchase totals =	$826.70		$916.1954	$916.20	$916.20	$916.10