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	$250.54	9.773%	$275.0253	$275.03	$275.05	$275.00
Purchase #2	$127.53	10.771%	$141.2663	$141.27	$141.25	$141.30
Purchase #3	$218.79	4.582%	$228.815	$228.82	$228.80	$228.80
Purchase #4	$82.59	7.485%	$88.7719	$88.77	$88.75	$88.80
Purchase #5	$151.98	6.501%	$161.8602	$161.86	$161.85	$161.90
Purchase #6	$238.60	6.420%	$253.9181	$253.92	$253.90	$253.90
Purchase #7	$156.82	4.834%	$164.4007	$164.40	$164.40	$164.40
7 purchase totals =	$1,226.85		$1,314.0575	$1,314.07	$1,314.00	$1,314.10