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	$57.53	3.805%	$59.719	$59.72	$59.70	$59.70
Purchase #2	$31.90	8.756%	$34.6932	$34.69	$34.70	$34.70
Purchase #3	$156.86	4.772%	$164.3454	$164.35	$164.35	$164.30
Purchase #4	$102.59	3.740%	$106.4269	$106.43	$106.45	$106.40
Purchase #5	$84.37	10.714%	$93.4094	$93.41	$93.40	$93.40
Purchase #6	$228.75	11.614%	$255.317	$255.32	$255.30	$255.30
Purchase #7	$195.59	9.824%	$214.8048	$214.80	$214.80	$214.80
7 purchase totals =	$857.59		$928.7157	$928.72	$928.70	$928.60