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	$119.76	12.125%	$134.2809	$134.28	$134.30	$134.30
Purchase #2	$65.93	10.555%	$72.8889	$72.89	$72.90	$72.90
Purchase #3	$93.67	6.120%	$99.4026	$99.40	$99.40	$99.40
Purchase #4	$122.32	9.674%	$134.1532	$134.15	$134.15	$134.20
Purchase #5	$152.33	13.719%	$173.2282	$173.23	$173.25	$173.20
Purchase #6	$149.94	4.459%	$156.6258	$156.63	$156.65	$156.60
Purchase #7	$232.78	5.147%	$244.7612	$244.76	$244.75	$244.80
7 purchase totals =	$936.73		$1,015.3408	$1,015.34	$1,015.40	$1,015.40