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	$214.55	3.768%	$222.6342	$222.63	$222.65	$222.60
Purchase #2	$57.36	13.344%	$65.0141	$65.01	$65.00	$65.00
Purchase #3	$80.53	3.155%	$83.0707	$83.07	$83.05	$83.10
Purchase #4	$115.46	13.235%	$130.7411	$130.74	$130.75	$130.70
Purchase #5	$70.36	12.150%	$78.9087	$78.91	$78.90	$78.90
Purchase #6	$91.63	7.316%	$98.3337	$98.33	$98.35	$98.30
Purchase #7	$39.63	5.409%	$41.7736	$41.77	$41.75	$41.80
7 purchase totals =	$669.52		$720.4761	$720.46	$720.45	$720.40