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	$148.67	13.832%	$169.234	$169.23	$169.25	$169.20
Purchase #2	$96.66	13.516%	$109.7246	$109.72	$109.70	$109.70
Purchase #3	$118.72	11.842%	$132.7788	$132.78	$132.80	$132.80
Purchase #4	$194.66	12.830%	$219.6349	$219.63	$219.65	$219.60
Purchase #5	$216.59	11.427%	$241.3397	$241.34	$241.35	$241.30
Purchase #6	$84.56	8.648%	$91.8727	$91.87	$91.85	$91.90
Purchase #7	$204.56	8.690%	$222.3363	$222.34	$222.35	$222.30
7 purchase totals =	$1,064.42		$1,186.9210	$1,186.91	$1,186.95	$1,186.80