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	$197.49	6.237%	$209.8075	$209.81	$209.80	$209.80
Purchase #2	$21.59	11.844%	$24.1471	$24.15	$24.15	$24.10
Purchase #3	$187.51	4.805%	$196.5199	$196.52	$196.50	$196.50
Purchase #4	$72.67	6.732%	$77.5621	$77.56	$77.55	$77.60
Purchase #5	$123.79	7.190%	$132.6905	$132.69	$132.70	$132.70
Purchase #6	$245.57	5.833%	$259.8941	$259.89	$259.90	$259.90
Purchase #7	$128.34	4.801%	$134.5016	$134.50	$134.50	$134.50
7 purchase totals =	$976.96		$1,035.1228	$1,035.12	$1,035.10	$1,035.10