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	$73.50	10.304%	$81.0734	$81.07	$81.05	$81.10
Purchase #2	$243.52	4.841%	$255.3088	$255.31	$255.30	$255.30
Purchase #3	$203.34	7.565%	$218.7227	$218.72	$218.70	$218.70
Purchase #4	$96.81	9.129%	$105.6478	$105.65	$105.65	$105.60
Purchase #5	$215.82	5.767%	$228.2663	$228.27	$228.25	$228.30
Purchase #6	$46.92	8.377%	$50.8505	$50.85	$50.85	$50.90
Purchase #7	$74.82	11.516%	$83.4363	$83.44	$83.45	$83.40
7 purchase totals =	$954.73		$1,023.3058	$1,023.31	$1,023.25	$1,023.30