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	$156.91	5.169%	$165.0207	$165.02	$165.00	$165.00
Purchase #2	$187.90	4.553%	$196.4551	$196.46	$196.45	$196.50
Purchase #3	$54.99	8.837%	$59.8495	$59.85	$59.85	$59.80
Purchase #4	$230.26	6.606%	$245.471	$245.47	$245.45	$245.50
Purchase #5	$132.42	3.431%	$136.9633	$136.96	$136.95	$137.00
Purchase #6	$42.96	12.588%	$48.3678	$48.37	$48.35	$48.40
Purchase #7	$175.53	13.430%	$199.1037	$199.10	$199.10	$199.10
7 purchase totals =	$980.97		$1,051.2311	$1,051.23	$1,051.15	$1,051.30