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	$29.86	10.454%	$32.9816	$32.98	$33.00	$33.00
Purchase #2	$67.82	12.171%	$76.0744	$76.07	$76.05	$76.10
Purchase #3	$195.79	12.130%	$219.5393	$219.54	$219.55	$219.50
Purchase #4	$150.69	13.730%	$171.3797	$171.38	$171.40	$171.40
Purchase #5	$236.33	11.730%	$264.0515	$264.05	$264.05	$264.10
Purchase #6	$112.33	9.567%	$123.0766	$123.08	$123.10	$123.10
Purchase #7	$125.52	10.743%	$139.0046	$139.00	$139.00	$139.00
7 purchase totals =	$918.34		$1,026.1077	$1,026.10	$1,026.15	$1,026.20