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	$92.72	10.790%	$102.7245	$102.72	$102.70	$102.70
Purchase #2	$86.65	6.115%	$91.9486	$91.95	$91.95	$91.90
Purchase #3	$140.30	5.156%	$147.5339	$147.53	$147.55	$147.50
Purchase #4	$78.63	13.380%	$89.1507	$89.15	$89.15	$89.20
Purchase #5	$23.64	6.792%	$25.2456	$25.25	$25.25	$25.20
Purchase #6	$77.81	3.502%	$80.5349	$80.53	$80.55	$80.50
Purchase #7	$246.57	3.537%	$255.2912	$255.29	$255.30	$255.30
7 purchase totals =	$746.32		$792.4294	$792.42	$792.45	$792.30