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	$152.50	3.655%	$158.0739	$158.07	$158.05	$158.10
Purchase #2	$59.88	3.774%	$62.1399	$62.14	$62.15	$62.10
Purchase #3	$64.65	11.268%	$71.9348	$71.93	$71.95	$71.90
Purchase #4	$83.95	10.811%	$93.0258	$93.03	$93.05	$93.00
Purchase #5	$94.41	11.194%	$104.9783	$104.98	$105.00	$105.00
Purchase #6	$244.56	13.517%	$277.6172	$277.62	$277.60	$277.60
Purchase #7	$28.61	9.460%	$31.3165	$31.32	$31.30	$31.30
7 purchase totals =	$728.56		$799.0864	$799.09	$799.10	$799.00