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	$140.75	11.514%	$156.956	$156.96	$156.95	$157.00
Purchase #2	$172.46	4.280%	$179.8413	$179.84	$179.85	$179.80
Purchase #3	$125.25	4.225%	$130.5418	$130.54	$130.55	$130.50
Purchase #4	$6.89	11.799%	$7.703	$7.70	$7.70	$7.70
Purchase #5	$55.33	4.333%	$57.7274	$57.73	$57.75	$57.70
Purchase #6	$19.39	3.603%	$20.0886	$20.09	$20.10	$20.10
Purchase #7	$208.39	9.256%	$227.6786	$227.68	$227.70	$227.70
7 purchase totals =	$728.46		$780.5367	$780.54	$780.60	$780.50