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	$96.99	10.470%	$107.1449	$107.14	$107.15	$107.10
Purchase #2	$79.41	4.116%	$82.6785	$82.68	$82.70	$82.70
Purchase #3	$143.91	6.821%	$153.7261	$153.73	$153.75	$153.70
Purchase #4	$137.52	6.546%	$146.5221	$146.52	$146.50	$146.50
Purchase #5	$214.40	11.645%	$239.3669	$239.37	$239.35	$239.40
Purchase #6	$131.26	13.425%	$148.8817	$148.88	$148.90	$148.90
Purchase #7	$118.47	4.294%	$123.5571	$123.56	$123.55	$123.60
7 purchase totals =	$921.96		$1,001.8773	$1,001.88	$1,001.90	$1,001.90