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	$206.40	12.465%	$232.1278	$232.13	$232.15	$232.10
Purchase #2	$234.39	5.506%	$247.2955	$247.30	$247.30	$247.30
Purchase #3	$90.71	4.222%	$94.5398	$94.54	$94.55	$94.50
Purchase #4	$80.75	10.411%	$89.1569	$89.16	$89.15	$89.20
Purchase #5	$110.71	7.364%	$118.8627	$118.86	$118.85	$118.90
Purchase #6	$91.76	7.223%	$98.3878	$98.39	$98.40	$98.40
Purchase #7	$190.39	5.634%	$201.1166	$201.12	$201.10	$201.10
7 purchase totals =	$1,005.11		$1,081.4871	$1,081.50	$1,081.50	$1,081.50