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	$100.82	7.183%	$108.0619	$108.06	$108.05	$108.10
Purchase #2	$91.85	4.847%	$96.302	$96.30	$96.30	$96.30
Purchase #3	$95.43	13.853%	$108.6499	$108.65	$108.65	$108.60
Purchase #4	$192.85	12.350%	$216.667	$216.67	$216.65	$216.70
Purchase #5	$182.90	9.773%	$200.7748	$200.77	$200.75	$200.80
Purchase #6	$85.97	4.625%	$89.9461	$89.95	$89.95	$89.90
Purchase #7	$236.56	4.111%	$246.285	$246.29	$246.30	$246.30
7 purchase totals =	$986.38		$1,066.6867	$1,066.69	$1,066.65	$1,066.70