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	$191.72	12.109%	$214.9354	$214.94	$214.95	$214.90
Purchase #2	$135.46	13.259%	$153.4206	$153.42	$153.40	$153.40
Purchase #3	$149.28	10.692%	$165.241	$165.24	$165.25	$165.20
Purchase #4	$89.85	5.757%	$95.0227	$95.02	$95.00	$95.00
Purchase #5	$180.64	8.650%	$196.2654	$196.27	$196.25	$196.30
Purchase #6	$174.94	3.522%	$181.1014	$181.10	$181.10	$181.10
Purchase #7	$126.91	7.521%	$136.4549	$136.45	$136.45	$136.50
7 purchase totals =	$1,048.80		$1,142.4414	$1,142.44	$1,142.40	$1,142.40