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	$135.45	9.853%	$148.7959	$148.80	$148.80	$148.80
Purchase #2	$194.59	11.329%	$216.6351	$216.64	$216.65	$216.60
Purchase #3	$196.71	11.692%	$219.7093	$219.71	$219.70	$219.70
Purchase #4	$100.27	4.522%	$104.8042	$104.80	$104.80	$104.80
Purchase #5	$73.51	5.370%	$77.4575	$77.46	$77.45	$77.50
Purchase #6	$181.27	5.524%	$191.2834	$191.28	$191.30	$191.30
Purchase #7	$130.91	9.362%	$143.1658	$143.17	$143.15	$143.20
7 purchase totals =	$1,012.71		$1,101.8512	$1,101.86	$1,101.85	$1,101.90