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	$155.98	12.565%	$175.5789	$175.58	$175.60	$175.60
Purchase #2	$167.27	3.320%	$172.8234	$172.82	$172.80	$172.80
Purchase #3	$57.97	11.639%	$64.7171	$64.72	$64.70	$64.70
Purchase #4	$32.39	3.173%	$33.4177	$33.42	$33.40	$33.40
Purchase #5	$113.57	4.344%	$118.5035	$118.50	$118.50	$118.50
Purchase #6	$193.38	6.746%	$206.4254	$206.43	$206.45	$206.40
Purchase #7	$12.91	7.354%	$13.8594	$13.86	$13.85	$13.90
7 purchase totals =	$733.47		$785.3254	$785.33	$785.30	$785.30