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	$72.67	8.306%	$78.706	$78.71	$78.70	$78.70
Purchase #2	$55.83	4.374%	$58.272	$58.27	$58.25	$58.30
Purchase #3	$19.67	9.322%	$21.5036	$21.50	$21.50	$21.50
Purchase #4	$106.94	4.385%	$111.6293	$111.63	$111.65	$111.60
Purchase #5	$104.37	7.483%	$112.18	$112.18	$112.20	$112.20
Purchase #6	$236.92	4.158%	$246.7711	$246.77	$246.75	$246.80
Purchase #7	$30.98	10.312%	$34.1747	$34.17	$34.15	$34.20
7 purchase totals =	$627.38		$663.2367	$663.23	$663.20	$663.30