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	$193.43	5.656%	$204.3704	$204.37	$204.35	$204.40
Purchase #2	$249.74	8.640%	$271.3175	$271.32	$271.30	$271.30
Purchase #3	$175.28	7.756%	$188.8747	$188.87	$188.85	$188.90
Purchase #4	$145.37	12.834%	$164.0268	$164.03	$164.05	$164.00
Purchase #5	$134.59	5.215%	$141.6089	$141.61	$141.60	$141.60
Purchase #6	$100.74	10.441%	$111.2583	$111.26	$111.25	$111.30
Purchase #7	$127.76	12.607%	$143.8667	$143.87	$143.85	$143.90
7 purchase totals =	$1,126.91		$1,225.3233	$1,225.33	$1,225.25	$1,225.40