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	$131.45	4.164%	$136.9236	$136.92	$136.90	$136.90
Purchase #2	$223.89	7.437%	$240.5407	$240.54	$240.55	$240.50
Purchase #3	$64.39	11.617%	$71.8702	$71.87	$71.85	$71.90
Purchase #4	$26.36	11.868%	$29.4884	$29.49	$29.50	$29.50
Purchase #5	$60.71	4.802%	$63.6253	$63.63	$63.65	$63.60
Purchase #6	$215.59	3.289%	$222.6808	$222.68	$222.70	$222.70
Purchase #7	$229.46	9.787%	$251.9173	$251.92	$251.90	$251.90
7 purchase totals =	$951.85		$1,017.0463	$1,017.05	$1,017.05	$1,017.00