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	$174.33	12.143%	$195.4989	$195.50	$195.50	$195.50
Purchase #2	$203.66	4.366%	$212.5518	$212.55	$212.55	$212.60
Purchase #3	$168.92	11.727%	$188.7292	$188.73	$188.75	$188.70
Purchase #4	$73.36	12.243%	$82.3415	$82.34	$82.35	$82.30
Purchase #5	$131.93	6.137%	$140.0265	$140.03	$140.05	$140.00
Purchase #6	$76.85	11.505%	$85.6916	$85.69	$85.70	$85.70
Purchase #7	$123.92	6.282%	$131.7047	$131.70	$131.70	$131.70
7 purchase totals =	$952.97		$1,036.5442	$1,036.54	$1,036.60	$1,036.50