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	$178.40	4.802%	$186.9668	$186.97	$186.95	$187.00
Purchase #2	$35.76	5.650%	$37.7804	$37.78	$37.80	$37.80
Purchase #3	$212.77	7.871%	$229.5171	$229.52	$229.50	$229.50
Purchase #4	$40.89	3.670%	$42.3907	$42.39	$42.40	$42.40
Purchase #5	$67.42	6.541%	$71.8299	$71.83	$71.85	$71.80
Purchase #6	$231.52	12.593%	$260.6753	$260.68	$260.70	$260.70
Purchase #7	$45.49	7.817%	$49.046	$49.05	$49.05	$49.00
7 purchase totals =	$812.25		$878.2062	$878.22	$878.25	$878.20