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	$132.81	11.844%	$148.54	$148.54	$148.55	$148.50
Purchase #2	$164.34	13.767%	$186.9647	$186.96	$186.95	$187.00
Purchase #3	$71.72	9.835%	$78.7737	$78.77	$78.75	$78.80
Purchase #4	$63.70	8.860%	$69.3438	$69.34	$69.35	$69.30
Purchase #5	$35.63	7.515%	$38.3076	$38.31	$38.30	$38.30
Purchase #6	$56.96	5.232%	$59.9401	$59.94	$59.95	$59.90
Purchase #7	$162.87	5.147%	$171.2529	$171.25	$171.25	$171.30
7 purchase totals =	$688.03		$753.1228	$753.11	$753.10	$753.10