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	$62.64	10.216%	$69.0393	$69.04	$69.05	$69.00
Purchase #2	$224.93	4.294%	$234.5885	$234.59	$234.60	$234.60
Purchase #3	$41.57	10.220%	$45.8185	$45.82	$45.80	$45.80
Purchase #4	$37.27	6.251%	$39.5997	$39.60	$39.60	$39.60
Purchase #5	$113.90	9.172%	$124.3469	$124.35	$124.35	$124.30
Purchase #6	$48.60	4.389%	$50.7331	$50.73	$50.75	$50.70
Purchase #7	$205.60	10.663%	$227.5231	$227.52	$227.50	$227.50
7 purchase totals =	$734.51		$791.6491	$791.65	$791.65	$791.50