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	$167.59	8.775%	$182.296	$182.30	$182.30	$182.30
Purchase #2	$177.49	10.852%	$196.7512	$196.75	$196.75	$196.80
Purchase #3	$29.32	11.161%	$32.5924	$32.59	$32.60	$32.60
Purchase #4	$142.73	11.790%	$159.5579	$159.56	$159.55	$159.60
Purchase #5	$139.25	4.236%	$145.1486	$145.15	$145.15	$145.10
Purchase #6	$200.78	11.408%	$223.685	$223.69	$223.70	$223.70
Purchase #7	$141.48	7.794%	$152.507	$152.51	$152.50	$152.50
7 purchase totals =	$998.64		$1,092.5381	$1,092.55	$1,092.55	$1,092.60