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	$35.46	6.275%	$37.6851	$37.69	$37.70	$37.70
Purchase #2	$55.51	10.144%	$61.1409	$61.14	$61.15	$61.10
Purchase #3	$166.28	8.493%	$180.4022	$180.40	$180.40	$180.40
Purchase #4	$215.59	6.349%	$229.2778	$229.28	$229.30	$229.30
Purchase #5	$250.29	4.490%	$261.528	$261.53	$261.55	$261.50
Purchase #6	$241.36	13.710%	$274.4505	$274.45	$274.45	$274.50
Purchase #7	$123.46	7.173%	$132.3158	$132.32	$132.30	$132.30
7 purchase totals =	$1,087.95		$1,176.8003	$1,176.81	$1,176.85	$1,176.80