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	$206.27	6.575%	$219.8323	$219.83	$219.85	$219.80
Purchase #2	$129.85	11.848%	$145.2346	$145.23	$145.25	$145.20
Purchase #3	$92.97	3.496%	$96.2202	$96.22	$96.20	$96.20
Purchase #4	$72.75	13.447%	$82.5327	$82.53	$82.55	$82.50
Purchase #5	$59.87	3.266%	$61.8254	$61.83	$61.85	$61.80
Purchase #6	$231.73	3.361%	$239.5184	$239.52	$239.50	$239.50
Purchase #7	$150.67	5.175%	$158.4672	$158.47	$158.45	$158.50
7 purchase totals =	$944.11		$1,003.6308	$1,003.63	$1,003.65	$1,003.50