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	$43.26	6.217%	$45.9495	$45.95	$45.95	$45.90
Purchase #2	$77.62	11.790%	$86.7714	$86.77	$86.75	$86.80
Purchase #3	$98.76	5.207%	$103.9024	$103.90	$103.90	$103.90
Purchase #4	$187.71	13.240%	$212.5628	$212.56	$212.55	$212.60
Purchase #5	$148.55	12.145%	$166.5914	$166.59	$166.60	$166.60
Purchase #6	$167.40	4.106%	$174.2734	$174.27	$174.25	$174.30
Purchase #7	$132.38	4.419%	$138.2299	$138.23	$138.25	$138.20
7 purchase totals =	$855.68		$928.2808	$928.27	$928.25	$928.30