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	$33.95	11.772%	$37.9466	$37.95	$37.95	$37.90
Purchase #2	$79.91	12.147%	$89.6167	$89.62	$89.60	$89.60
Purchase #3	$172.73	12.465%	$194.2608	$194.26	$194.25	$194.30
Purchase #4	$57.75	6.485%	$61.4951	$61.50	$61.50	$61.50
Purchase #5	$156.54	7.520%	$168.3118	$168.31	$168.30	$168.30
Purchase #6	$232.55	10.187%	$256.2399	$256.24	$256.25	$256.20
Purchase #7	$98.82	9.299%	$108.0093	$108.01	$108.00	$108.00
7 purchase totals =	$832.25		$915.8802	$915.89	$915.85	$915.80