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	$54.79	11.120%	$60.8826	$60.88	$60.90	$60.90
Purchase #2	$38.45	11.521%	$42.8798	$42.88	$42.90	$42.90
Purchase #3	$130.30	3.824%	$135.2827	$135.28	$135.30	$135.30
Purchase #4	$190.71	3.217%	$196.8451	$196.85	$196.85	$196.80
Purchase #5	$236.34	12.105%	$264.949	$264.95	$264.95	$264.90
Purchase #6	$192.28	7.227%	$206.1761	$206.18	$206.20	$206.20
Purchase #7	$18.95	11.400%	$21.1103	$21.11	$21.10	$21.10
7 purchase totals =	$861.82		$928.1256	$928.13	$928.20	$928.10