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	$74.53	6.719%	$79.5377	$79.54	$79.55	$79.50
Purchase #2	$208.46	9.399%	$228.0532	$228.05	$228.05	$228.10
Purchase #3	$118.39	12.199%	$132.8324	$132.83	$132.85	$132.80
Purchase #4	$105.58	6.584%	$112.5314	$112.53	$112.55	$112.50
Purchase #5	$144.31	5.531%	$152.2918	$152.29	$152.30	$152.30
Purchase #6	$191.31	9.155%	$208.8244	$208.82	$208.80	$208.80
Purchase #7	$148.42	6.644%	$158.281	$158.28	$158.30	$158.30
7 purchase totals =	$991.00		$1,072.3519	$1,072.34	$1,072.40	$1,072.30