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	$126.98	3.746%	$131.7367	$131.74	$131.75	$131.70
Purchase #2	$100.36	11.419%	$111.8201	$111.82	$111.80	$111.80
Purchase #3	$204.48	3.634%	$211.9108	$211.91	$211.90	$211.90
Purchase #4	$56.35	13.384%	$63.8919	$63.89	$63.90	$63.90
Purchase #5	$10.55	11.520%	$11.7654	$11.77	$11.75	$11.80
Purchase #6	$178.27	3.737%	$184.9319	$184.93	$184.95	$184.90
Purchase #7	$91.69	6.130%	$97.3106	$97.31	$97.30	$97.30
7 purchase totals =	$768.68		$813.3674	$813.37	$813.35	$813.30