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	$43.61	11.339%	$48.5549	$48.55	$48.55	$48.60
Purchase #2	$157.79	6.858%	$168.6112	$168.61	$168.60	$168.60
Purchase #3	$127.88	6.169%	$135.7689	$135.77	$135.75	$135.80
Purchase #4	$36.45	3.208%	$37.6193	$37.62	$37.60	$37.60
Purchase #5	$144.48	5.776%	$152.8252	$152.83	$152.85	$152.80
Purchase #6	$38.40	4.621%	$40.1745	$40.17	$40.15	$40.20
Purchase #7	$223.39	9.814%	$245.3135	$245.31	$245.30	$245.30
7 purchase totals =	$772.00		$828.8675	$828.86	$828.80	$828.90