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	$84.82	8.120%	$91.7074	$91.71	$91.70	$91.70
Purchase #2	$81.31	10.816%	$90.1045	$90.10	$90.10	$90.10
Purchase #3	$240.97	7.669%	$259.45	$259.45	$259.45	$259.50
Purchase #4	$75.53	3.588%	$78.24	$78.24	$78.25	$78.20
Purchase #5	$223.88	6.446%	$238.3113	$238.31	$238.30	$238.30
Purchase #6	$61.37	4.114%	$63.8948	$63.89	$63.90	$63.90
Purchase #7	$108.90	6.648%	$116.1397	$116.14	$116.15	$116.10
7 purchase totals =	$876.78		$937.8477	$937.84	$937.85	$937.80