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	$66.52	9.411%	$72.7802	$72.78	$72.80	$72.80
Purchase #2	$217.47	5.653%	$229.7636	$229.76	$229.75	$229.80
Purchase #3	$53.79	11.439%	$59.943	$59.94	$59.95	$59.90
Purchase #4	$165.27	7.410%	$177.5165	$177.52	$177.50	$177.50
Purchase #5	$101.91	3.803%	$105.7856	$105.79	$105.80	$105.80
Purchase #6	$60.41	6.150%	$64.1252	$64.13	$64.15	$64.10
Purchase #7	$20.84	10.275%	$22.9813	$22.98	$23.00	$23.00
7 purchase totals =	$686.21		$732.8954	$732.90	$732.95	$732.90