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	$72.88	5.490%	$76.8811	$76.88	$76.90	$76.90
Purchase #2	$18.76	7.405%	$20.1492	$20.15	$20.15	$20.10
Purchase #3	$154.29	8.717%	$167.7395	$167.74	$167.75	$167.70
Purchase #4	$233.33	13.387%	$264.5659	$264.57	$264.55	$264.60
Purchase #5	$139.63	11.553%	$155.7615	$155.76	$155.75	$155.80
Purchase #6	$156.37	5.536%	$165.0266	$165.03	$165.05	$165.00
Purchase #7	$13.46	5.365%	$14.1821	$14.18	$14.20	$14.20
7 purchase totals =	$788.72		$864.3059	$864.31	$864.35	$864.30