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	$158.70	3.368%	$164.045	$164.05	$164.05	$164.00
Purchase #2	$60.46	4.419%	$63.1317	$63.13	$63.15	$63.10
Purchase #3	$216.80	8.117%	$234.3977	$234.40	$234.40	$234.40
Purchase #4	$55.31	3.567%	$57.2829	$57.28	$57.30	$57.30
Purchase #5	$38.30	8.231%	$41.4525	$41.45	$41.45	$41.50
Purchase #6	$242.72	10.167%	$267.3973	$267.40	$267.40	$267.40
Purchase #7	$238.89	12.533%	$268.8301	$268.83	$268.85	$268.80
7 purchase totals =	$1,011.18		$1,096.5372	$1,096.54	$1,096.60	$1,096.50