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	$35.86	4.810%	$37.5849	$37.58	$37.60	$37.60
Purchase #2	$37.59	9.397%	$41.1223	$41.12	$41.10	$41.10
Purchase #3	$199.31	6.737%	$212.7375	$212.74	$212.75	$212.70
Purchase #4	$93.35	6.661%	$99.568	$99.57	$99.55	$99.60
Purchase #5	$54.95	10.251%	$60.5829	$60.58	$60.60	$60.60
Purchase #6	$118.88	7.691%	$128.0231	$128.02	$128.00	$128.00
Purchase #7	$168.51	6.755%	$179.8929	$179.89	$179.90	$179.90
7 purchase totals =	$708.45		$759.5116	$759.50	$759.50	$759.50