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	$173.52	5.205%	$182.5517	$182.55	$182.55	$182.60
Purchase #2	$124.30	10.492%	$137.3416	$137.34	$137.35	$137.30
Purchase #3	$79.86	7.842%	$86.1226	$86.12	$86.10	$86.10
Purchase #4	$98.37	10.804%	$108.9979	$109.00	$109.00	$109.00
Purchase #5	$214.55	12.673%	$241.7399	$241.74	$241.75	$241.70
Purchase #6	$160.89	4.827%	$168.6562	$168.66	$168.65	$168.70
Purchase #7	$233.89	3.512%	$242.1042	$242.10	$242.10	$242.10
7 purchase totals =	$1,085.38		$1,167.5141	$1,167.51	$1,167.50	$1,167.50