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	$55.33	7.466%	$59.4609	$59.46	$59.45	$59.50
Purchase #2	$204.53	8.565%	$222.048	$222.05	$222.05	$222.00
Purchase #3	$229.27	8.746%	$249.322	$249.32	$249.30	$249.30
Purchase #4	$100.63	8.739%	$109.4241	$109.42	$109.40	$109.40
Purchase #5	$112.35	7.855%	$121.1751	$121.18	$121.20	$121.20
Purchase #6	$120.70	3.210%	$124.5745	$124.57	$124.55	$124.60
Purchase #7	$248.25	8.524%	$269.4108	$269.41	$269.40	$269.40
7 purchase totals =	$1,071.06		$1,155.4154	$1,155.41	$1,155.35	$1,155.40