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	$229.34	6.117%	$243.3687	$243.37	$243.35	$243.40
Purchase #2	$157.37	9.692%	$172.6223	$172.62	$172.60	$172.60
Purchase #3	$79.67	3.783%	$82.6839	$82.68	$82.70	$82.70
Purchase #4	$191.51	6.428%	$203.8203	$203.82	$203.80	$203.80
Purchase #5	$238.26	4.813%	$249.7275	$249.73	$249.75	$249.70
Purchase #6	$145.68	13.522%	$165.3788	$165.38	$165.40	$165.40
Purchase #7	$110.88	11.699%	$123.8519	$123.85	$123.85	$123.90
7 purchase totals =	$1,152.71		$1,241.4534	$1,241.45	$1,241.45	$1,241.50