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	$41.90	4.674%	$43.8584	$43.86	$43.85	$43.90
Purchase #2	$144.78	13.370%	$164.1371	$164.14	$164.15	$164.10
Purchase #3	$49.90	13.602%	$56.6874	$56.69	$56.70	$56.70
Purchase #4	$120.41	13.230%	$136.3402	$136.34	$136.35	$136.30
Purchase #5	$127.43	5.251%	$134.1213	$134.12	$134.10	$134.10
Purchase #6	$185.75	13.781%	$211.3482	$211.35	$211.35	$211.30
Purchase #7	$212.40	10.507%	$234.7169	$234.72	$234.70	$234.70
7 purchase totals =	$882.57		$981.2095	$981.22	$981.20	$981.10