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	$96.72	8.478%	$104.9199	$104.92	$104.90	$104.90
Purchase #2	$162.82	8.799%	$177.1465	$177.15	$177.15	$177.10
Purchase #3	$59.74	12.726%	$67.3425	$67.34	$67.35	$67.30
Purchase #4	$211.65	10.344%	$233.5431	$233.54	$233.55	$233.50
Purchase #5	$245.31	12.865%	$276.8691	$276.87	$276.85	$276.90
Purchase #6	$222.70	5.311%	$234.5276	$234.53	$234.55	$234.50
Purchase #7	$89.75	7.560%	$96.5351	$96.54	$96.55	$96.50
7 purchase totals =	$1,088.69		$1,190.8838	$1,190.89	$1,190.90	$1,190.70