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	$79.62	4.181%	$82.9489	$82.95	$82.95	$82.90
Purchase #2	$87.81	10.269%	$96.8272	$96.83	$96.85	$96.80
Purchase #3	$195.79	5.559%	$206.674	$206.67	$206.65	$206.70
Purchase #4	$189.77	10.636%	$209.9539	$209.95	$209.95	$210.00
Purchase #5	$232.65	13.223%	$263.4133	$263.41	$263.40	$263.40
Purchase #6	$125.53	4.613%	$131.3207	$131.32	$131.30	$131.30
Purchase #7	$124.70	12.614%	$140.4297	$140.43	$140.45	$140.40
7 purchase totals =	$1,035.87		$1,131.5677	$1,131.56	$1,131.55	$1,131.50