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	$56.69	10.119%	$62.4265	$62.43	$62.45	$62.40
Purchase #2	$35.39	8.230%	$38.3026	$38.30	$38.30	$38.30
Purchase #3	$181.35	5.254%	$190.8781	$190.88	$190.90	$190.90
Purchase #4	$114.73	13.773%	$130.5318	$130.53	$130.55	$130.50
Purchase #5	$83.92	11.318%	$93.4181	$93.42	$93.40	$93.40
Purchase #6	$113.61	10.775%	$125.8515	$125.85	$125.85	$125.90
Purchase #7	$97.82	8.164%	$105.806	$105.81	$105.80	$105.80
7 purchase totals =	$683.51		$747.2146	$747.22	$747.25	$747.20