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	$207.43	11.522%	$231.3301	$231.33	$231.35	$231.30
Purchase #2	$134.89	12.261%	$151.4289	$151.43	$151.45	$151.40
Purchase #3	$219.69	11.148%	$244.181	$244.18	$244.20	$244.20
Purchase #4	$12.62	12.321%	$14.1749	$14.17	$14.15	$14.20
Purchase #5	$178.27	4.860%	$186.9339	$186.93	$186.95	$186.90
Purchase #6	$81.49	13.818%	$92.7503	$92.75	$92.75	$92.80
Purchase #7	$159.53	12.352%	$179.2351	$179.24	$179.25	$179.20
7 purchase totals =	$993.92		$1,100.0342	$1,100.03	$1,100.10	$1,100.00