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	$226.39	8.134%	$244.8046	$244.80	$244.80	$244.80
Purchase #2	$101.68	9.688%	$111.5308	$111.53	$111.55	$111.50
Purchase #3	$6.25	8.642%	$6.7901	$6.79	$6.80	$6.80
Purchase #4	$111.74	13.760%	$127.1154	$127.12	$127.10	$127.10
Purchase #5	$148.78	12.588%	$167.5084	$167.51	$167.50	$167.50
Purchase #6	$98.61	13.722%	$112.1413	$112.14	$112.15	$112.10
Purchase #7	$36.79	4.620%	$38.4897	$38.49	$38.50	$38.50
7 purchase totals =	$730.24		$808.3803	$808.38	$808.40	$808.30