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	$195.70	6.485%	$208.3911	$208.39	$208.40	$208.40
Purchase #2	$155.38	7.814%	$167.5214	$167.52	$167.50	$167.50
Purchase #3	$156.66	4.572%	$163.8225	$163.82	$163.80	$163.80
Purchase #4	$35.37	5.550%	$37.333	$37.33	$37.35	$37.30
Purchase #5	$123.38	4.430%	$128.8457	$128.85	$128.85	$128.80
Purchase #6	$76.83	13.118%	$86.9086	$86.91	$86.90	$86.90
Purchase #7	$210.38	7.112%	$225.3422	$225.34	$225.35	$225.30
7 purchase totals =	$953.70		$1,018.1645	$1,018.16	$1,018.15	$1,018.00