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	$205.83	13.264%	$233.1313	$233.13	$233.15	$233.10
Purchase #2	$191.97	13.436%	$217.7631	$217.76	$217.75	$217.80
Purchase #3	$217.94	8.411%	$236.2709	$236.27	$236.25	$236.30
Purchase #4	$41.50	8.610%	$45.0732	$45.07	$45.05	$45.10
Purchase #5	$232.26	5.412%	$244.8299	$244.83	$244.85	$244.80
Purchase #6	$98.98	12.714%	$111.5643	$111.56	$111.55	$111.60
Purchase #7	$80.28	13.668%	$91.2527	$91.25	$91.25	$91.30
7 purchase totals =	$1,068.76		$1,179.8854	$1,179.87	$1,179.85	$1,180.00