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	$247.59	6.767%	$264.3444	$264.34	$264.35	$264.30
Purchase #2	$55.41	3.624%	$57.4181	$57.42	$57.40	$57.40
Purchase #3	$131.61	8.150%	$142.3362	$142.34	$142.35	$142.30
Purchase #4	$81.48	10.778%	$90.2619	$90.26	$90.25	$90.30
Purchase #5	$232.26	6.654%	$247.7146	$247.71	$247.70	$247.70
Purchase #6	$171.66	6.514%	$182.8419	$182.84	$182.85	$182.80
Purchase #7	$119.28	3.754%	$123.7578	$123.76	$123.75	$123.80
7 purchase totals =	$1,039.29		$1,108.6749	$1,108.67	$1,108.65	$1,108.60