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	$118.79	9.741%	$130.3613	$130.36	$130.35	$130.40
Purchase #2	$196.55	10.163%	$216.5254	$216.53	$216.55	$216.50
Purchase #3	$162.31	12.591%	$182.7465	$182.75	$182.75	$182.70
Purchase #4	$57.82	7.483%	$62.1467	$62.15	$62.15	$62.10
Purchase #5	$56.73	5.386%	$59.7855	$59.79	$59.80	$59.80
Purchase #6	$78.87	5.116%	$82.905	$82.91	$82.90	$82.90
Purchase #7	$214.95	12.776%	$242.412	$242.41	$242.40	$242.40
7 purchase totals =	$886.02		$976.8824	$976.90	$976.90	$976.80