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	$152.87	7.764%	$164.7388	$164.74	$164.75	$164.70
Purchase #2	$186.83	10.667%	$206.7592	$206.76	$206.75	$206.80
Purchase #3	$125.53	11.113%	$139.4801	$139.48	$139.50	$139.50
Purchase #4	$179.27	5.323%	$188.8125	$188.81	$188.80	$188.80
Purchase #5	$59.34	5.712%	$62.7295	$62.73	$62.75	$62.70
Purchase #6	$145.63	3.132%	$150.1911	$150.19	$150.20	$150.20
Purchase #7	$180.30	8.764%	$196.1015	$196.10	$196.10	$196.10
7 purchase totals =	$1,029.77		$1,108.8127	$1,108.81	$1,108.85	$1,108.80