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	$35.33	4.841%	$37.0403	$37.04	$37.05	$37.00
Purchase #2	$158.41	10.443%	$174.9528	$174.95	$174.95	$175.00
Purchase #3	$228.40	6.640%	$243.5658	$243.57	$243.55	$243.60
Purchase #4	$243.80	9.772%	$267.6241	$267.62	$267.60	$267.60
Purchase #5	$47.82	11.507%	$53.3226	$53.32	$53.30	$53.30
Purchase #6	$39.32	12.278%	$44.1477	$44.15	$44.15	$44.10
Purchase #7	$5.65	4.345%	$5.8955	$5.90	$5.90	$5.90
7 purchase totals =	$758.73		$826.5488	$826.55	$826.50	$826.50