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	$63.91	3.690%	$66.2683	$66.27	$66.25	$66.30
Purchase #2	$170.36	5.636%	$179.9615	$179.96	$179.95	$180.00
Purchase #3	$133.61	4.152%	$139.1575	$139.16	$139.15	$139.20
Purchase #4	$72.68	8.210%	$78.647	$78.65	$78.65	$78.60
Purchase #5	$221.56	7.106%	$237.3041	$237.30	$237.30	$237.30
Purchase #6	$136.61	11.842%	$152.7874	$152.79	$152.80	$152.80
Purchase #7	$212.70	8.656%	$231.1113	$231.11	$231.10	$231.10
7 purchase totals =	$1,011.43		$1,085.2371	$1,085.24	$1,085.20	$1,085.30