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	$61.32	4.592%	$64.1358	$64.14	$64.15	$64.10
Purchase #2	$219.58	5.572%	$231.815	$231.82	$231.80	$231.80
Purchase #3	$65.80	7.447%	$70.7001	$70.70	$70.70	$70.70
Purchase #4	$91.81	13.858%	$104.533	$104.53	$104.55	$104.50
Purchase #5	$68.61	13.843%	$78.1077	$78.11	$78.10	$78.10
Purchase #6	$231.56	13.539%	$262.9109	$262.91	$262.90	$262.90
Purchase #7	$86.25	12.262%	$96.826	$96.83	$96.85	$96.80
7 purchase totals =	$824.93		$909.0285	$909.04	$909.05	$908.90