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	$119.79	8.447%	$129.9087	$129.91	$129.90	$129.90
Purchase #2	$10.76	7.390%	$11.5552	$11.56	$11.55	$11.60
Purchase #3	$140.59	6.580%	$149.8408	$149.84	$149.85	$149.80
Purchase #4	$197.32	4.309%	$205.8225	$205.82	$205.80	$205.80
Purchase #5	$215.98	13.638%	$245.4354	$245.44	$245.45	$245.40
Purchase #6	$92.83	7.144%	$99.4618	$99.46	$99.45	$99.50
Purchase #7	$144.89	13.550%	$164.5226	$164.52	$164.50	$164.50
7 purchase totals =	$922.16		$1,006.5470	$1,006.55	$1,006.50	$1,006.50