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	$33.45	12.282%	$37.5583	$37.56	$37.55	$37.60
Purchase #2	$30.98	9.182%	$33.8246	$33.82	$33.80	$33.80
Purchase #3	$67.63	13.251%	$76.5917	$76.59	$76.60	$76.60
Purchase #4	$103.64	10.801%	$114.8342	$114.83	$114.85	$114.80
Purchase #5	$152.58	9.220%	$166.6479	$166.65	$166.65	$166.60
Purchase #6	$72.79	11.638%	$81.2613	$81.26	$81.25	$81.30
Purchase #7	$195.75	10.779%	$216.8499	$216.85	$216.85	$216.80
7 purchase totals =	$656.82		$727.5679	$727.56	$727.55	$727.50