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	$175.30	12.474%	$197.1669	$197.17	$197.15	$197.20
Purchase #2	$119.78	6.731%	$127.8424	$127.84	$127.85	$127.80
Purchase #3	$193.88	11.404%	$215.9901	$215.99	$216.00	$216.00
Purchase #4	$76.25	7.686%	$82.1106	$82.11	$82.10	$82.10
Purchase #5	$135.56	11.675%	$151.3866	$151.39	$151.40	$151.40
Purchase #6	$166.35	7.802%	$179.3286	$179.33	$179.35	$179.30
Purchase #7	$210.57	8.554%	$228.5822	$228.58	$228.60	$228.60
7 purchase totals =	$1,077.69		$1,182.4074	$1,182.41	$1,182.45	$1,182.40