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	$58.81	13.587%	$66.8005	$66.80	$66.80	$66.80
Purchase #2	$180.67	4.562%	$188.9122	$188.91	$188.90	$188.90
Purchase #3	$183.97	4.672%	$192.5651	$192.57	$192.55	$192.60
Purchase #4	$236.55	3.821%	$245.5886	$245.59	$245.60	$245.60
Purchase #5	$230.72	7.355%	$247.6895	$247.69	$247.70	$247.70
Purchase #6	$69.31	4.593%	$72.4934	$72.49	$72.50	$72.50
Purchase #7	$135.82	13.696%	$154.4219	$154.42	$154.40	$154.40
7 purchase totals =	$1,095.85		$1,168.4712	$1,168.47	$1,168.45	$1,168.50