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	$207.93	10.121%	$228.9746	$228.97	$228.95	$229.00
Purchase #2	$64.49	13.841%	$73.4161	$73.42	$73.40	$73.40
Purchase #3	$67.72	12.470%	$76.1647	$76.16	$76.15	$76.20
Purchase #4	$64.85	11.818%	$72.514	$72.51	$72.50	$72.50
Purchase #5	$29.91	4.107%	$31.1384	$31.14	$31.15	$31.10
Purchase #6	$222.56	9.576%	$243.8723	$243.87	$243.85	$243.90
Purchase #7	$145.87	6.472%	$155.3107	$155.31	$155.30	$155.30
7 purchase totals =	$803.33		$881.3908	$881.38	$881.30	$881.40