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	$145.87	11.257%	$162.2906	$162.29	$162.30	$162.30
Purchase #2	$143.45	7.215%	$153.7999	$153.80	$153.80	$153.80
Purchase #3	$246.98	5.112%	$259.6056	$259.61	$259.60	$259.60
Purchase #4	$19.49	5.238%	$20.5109	$20.51	$20.50	$20.50
Purchase #5	$104.66	4.243%	$109.1007	$109.10	$109.10	$109.10
Purchase #6	$75.85	12.213%	$85.1136	$85.11	$85.10	$85.10
Purchase #7	$223.39	10.781%	$247.4737	$247.47	$247.45	$247.50
7 purchase totals =	$959.69		$1,037.8950	$1,037.89	$1,037.85	$1,037.90