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	$242.75	10.134%	$267.3503	$267.35	$267.35	$267.40
Purchase #2	$32.74	11.187%	$36.4026	$36.40	$36.40	$36.40
Purchase #3	$170.47	12.558%	$191.8776	$191.88	$191.90	$191.90
Purchase #4	$51.96	4.738%	$54.4219	$54.42	$54.40	$54.40
Purchase #5	$196.85	9.671%	$215.8874	$215.89	$215.90	$215.90
Purchase #6	$72.28	6.180%	$76.7469	$76.75	$76.75	$76.70
Purchase #7	$145.63	4.526%	$152.2212	$152.22	$152.20	$152.20
7 purchase totals =	$912.68		$994.9079	$994.91	$994.90	$994.90