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	$168.61	13.375%	$191.1616	$191.16	$191.15	$191.20
Purchase #2	$89.57	12.278%	$100.5674	$100.57	$100.55	$100.60
Purchase #3	$69.39	7.843%	$74.8323	$74.83	$74.85	$74.80
Purchase #4	$231.43	11.432%	$257.8871	$257.89	$257.90	$257.90
Purchase #5	$190.75	6.617%	$203.3719	$203.37	$203.35	$203.40
Purchase #6	$152.74	4.163%	$159.0986	$159.10	$159.10	$159.10
Purchase #7	$109.43	8.657%	$118.9034	$118.90	$118.90	$118.90
7 purchase totals =	$1,011.92		$1,105.8223	$1,105.82	$1,105.80	$1,105.90