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	$139.94	4.303%	$145.9616	$145.96	$145.95	$146.00
Purchase #2	$55.69	11.563%	$62.1294	$62.13	$62.15	$62.10
Purchase #3	$249.65	7.859%	$269.27	$269.27	$269.25	$269.30
Purchase #4	$248.29	12.676%	$279.7632	$279.76	$279.75	$279.80
Purchase #5	$42.40	7.197%	$45.4515	$45.45	$45.45	$45.50
Purchase #6	$44.28	7.380%	$47.5479	$47.55	$47.55	$47.50
Purchase #7	$119.64	5.301%	$125.9821	$125.98	$126.00	$126.00
7 purchase totals =	$899.89		$976.1057	$976.10	$976.10	$976.20