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	$160.51	4.842%	$168.2819	$168.28	$168.30	$168.30
Purchase #2	$32.61	12.464%	$36.6745	$36.67	$36.65	$36.70
Purchase #3	$188.41	4.526%	$196.9374	$196.94	$196.95	$196.90
Purchase #4	$221.32	13.472%	$251.1362	$251.14	$251.15	$251.10
Purchase #5	$152.46	13.362%	$172.8317	$172.83	$172.85	$172.80
Purchase #6	$46.48	5.303%	$48.9448	$48.94	$48.95	$48.90
Purchase #7	$191.56	9.355%	$209.4804	$209.48	$209.50	$209.50
7 purchase totals =	$993.35		$1,084.2869	$1,084.28	$1,084.35	$1,084.20