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	$185.74	3.673%	$192.5622	$192.56	$192.55	$192.60
Purchase #2	$54.77	12.259%	$61.4843	$61.48	$61.50	$61.50
Purchase #3	$22.33	4.152%	$23.2571	$23.26	$23.25	$23.30
Purchase #4	$222.70	5.452%	$234.8416	$234.84	$234.85	$234.80
Purchase #5	$42.93	13.814%	$48.8604	$48.86	$48.85	$48.90
Purchase #6	$211.47	13.700%	$240.4414	$240.44	$240.45	$240.40
Purchase #7	$128.70	12.209%	$144.413	$144.41	$144.40	$144.40
7 purchase totals =	$868.64		$945.8600	$945.85	$945.85	$945.90