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	$94.58	5.620%	$99.8954	$99.90	$99.90	$99.90
Purchase #2	$156.84	9.784%	$172.1852	$172.19	$172.20	$172.20
Purchase #3	$36.50	6.530%	$38.8835	$38.88	$38.90	$38.90
Purchase #4	$98.46	6.299%	$104.662	$104.66	$104.65	$104.70
Purchase #5	$10.98	6.272%	$11.6687	$11.67	$11.65	$11.70
Purchase #6	$101.75	5.244%	$107.0858	$107.09	$107.10	$107.10
Purchase #7	$84.37	6.458%	$89.8186	$89.82	$89.80	$89.80
7 purchase totals =	$583.48		$624.1992	$624.21	$624.20	$624.30