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	$129.31	13.532%	$146.8082	$146.81	$146.80	$146.80
Purchase #2	$236.97	3.555%	$245.3943	$245.39	$245.40	$245.40
Purchase #3	$189.75	3.737%	$196.841	$196.84	$196.85	$196.80
Purchase #4	$93.90	5.810%	$99.3556	$99.36	$99.35	$99.40
Purchase #5	$53.68	10.155%	$59.1312	$59.13	$59.15	$59.10
Purchase #6	$142.88	10.601%	$158.0267	$158.03	$158.05	$158.00
Purchase #7	$88.94	12.857%	$100.375	$100.38	$100.40	$100.40
7 purchase totals =	$935.43		$1,005.9320	$1,005.94	$1,006.00	$1,005.90