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	$33.34	13.204%	$37.7422	$37.74	$37.75	$37.70
Purchase #2	$5.84	5.827%	$6.1803	$6.18	$6.20	$6.20
Purchase #3	$45.27	7.342%	$48.5937	$48.59	$48.60	$48.60
Purchase #4	$115.38	11.861%	$129.0652	$129.07	$129.05	$129.10
Purchase #5	$73.50	13.268%	$83.252	$83.25	$83.25	$83.30
Purchase #6	$84.87	5.566%	$89.5939	$89.59	$89.60	$89.60
Purchase #7	$196.52	3.751%	$203.8915	$203.89	$203.90	$203.90
7 purchase totals =	$554.72		$598.3188	$598.31	$598.35	$598.40