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	$220.47	11.822%	$246.534	$246.53	$246.55	$246.50
Purchase #2	$85.86	4.732%	$89.9229	$89.92	$89.90	$89.90
Purchase #3	$122.40	3.852%	$127.1148	$127.11	$127.10	$127.10
Purchase #4	$209.91	8.640%	$228.0462	$228.05	$228.05	$228.00
Purchase #5	$134.96	10.279%	$148.8325	$148.83	$148.85	$148.80
Purchase #6	$94.58	10.219%	$104.2451	$104.25	$104.25	$104.20
Purchase #7	$87.91	11.495%	$98.0153	$98.02	$98.00	$98.00
7 purchase totals =	$956.09		$1,042.7108	$1,042.71	$1,042.70	$1,042.50