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	$73.76	10.528%	$81.5255	$81.53	$81.55	$81.50
Purchase #2	$226.38	13.281%	$256.4455	$256.45	$256.45	$256.40
Purchase #3	$86.33	5.579%	$91.1464	$91.15	$91.15	$91.10
Purchase #4	$220.63	5.145%	$231.9814	$231.98	$232.00	$232.00
Purchase #5	$136.42	8.409%	$147.8916	$147.89	$147.90	$147.90
Purchase #6	$209.75	11.159%	$233.156	$233.16	$233.15	$233.20
Purchase #7	$18.69	11.260%	$20.7945	$20.79	$20.80	$20.80
7 purchase totals =	$971.96		$1,062.9409	$1,062.95	$1,063.00	$1,062.90