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	$180.89	11.515%	$201.7195	$201.72	$201.70	$201.70
Purchase #2	$85.85	4.735%	$89.915	$89.92	$89.90	$89.90
Purchase #3	$33.78	12.318%	$37.941	$37.94	$37.95	$37.90
Purchase #4	$162.44	5.747%	$171.7754	$171.78	$171.80	$171.80
Purchase #5	$162.90	3.534%	$168.6569	$168.66	$168.65	$168.70
Purchase #6	$150.42	8.206%	$162.7635	$162.76	$162.75	$162.80
Purchase #7	$93.31	6.606%	$99.4741	$99.47	$99.45	$99.50
7 purchase totals =	$869.59		$932.2454	$932.25	$932.20	$932.30