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	$73.62	12.377%	$82.7319	$82.73	$82.75	$82.70
Purchase #2	$72.32	3.781%	$75.0544	$75.05	$75.05	$75.10
Purchase #3	$53.42	3.206%	$55.1326	$55.13	$55.15	$55.10
Purchase #4	$81.55	6.531%	$86.876	$86.88	$86.90	$86.90
Purchase #5	$102.86	6.542%	$109.5891	$109.59	$109.60	$109.60
Purchase #6	$53.55	7.790%	$57.7215	$57.72	$57.70	$57.70
Purchase #7	$146.30	9.171%	$159.7172	$159.72	$159.70	$159.70
7 purchase totals =	$583.62		$626.8227	$626.82	$626.85	$626.80