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	$169.82	3.590%	$175.9165	$175.92	$175.90	$175.90
Purchase #2	$82.94	13.615%	$94.2323	$94.23	$94.25	$94.20
Purchase #3	$39.74	3.332%	$41.0641	$41.06	$41.05	$41.10
Purchase #4	$82.38	12.664%	$92.8126	$92.81	$92.80	$92.80
Purchase #5	$69.80	3.679%	$72.3679	$72.37	$72.35	$72.40
Purchase #6	$127.48	7.183%	$136.6369	$136.64	$136.65	$136.60
Purchase #7	$90.57	7.370%	$97.245	$97.25	$97.25	$97.20
7 purchase totals =	$662.73		$710.2753	$710.28	$710.25	$710.20