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	$153.78	6.831%	$164.2847	$164.28	$164.30	$164.30
Purchase #2	$80.74	5.843%	$85.4576	$85.46	$85.45	$85.50
Purchase #3	$35.91	3.138%	$37.0369	$37.04	$37.05	$37.00
Purchase #4	$45.59	6.688%	$48.6391	$48.64	$48.65	$48.60
Purchase #5	$73.30	6.675%	$78.1928	$78.19	$78.20	$78.20
Purchase #6	$197.48	7.804%	$212.8913	$212.89	$212.90	$212.90
Purchase #7	$175.71	5.827%	$185.9486	$185.95	$185.95	$185.90
7 purchase totals =	$762.51		$812.4510	$812.45	$812.50	$812.40