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	$84.43	11.307%	$93.9765	$93.98	$94.00	$94.00
Purchase #2	$54.83	13.176%	$62.0544	$62.05	$62.05	$62.10
Purchase #3	$248.96	7.485%	$267.5947	$267.59	$267.60	$267.60
Purchase #4	$43.93	3.258%	$45.3612	$45.36	$45.35	$45.40
Purchase #5	$130.89	3.450%	$135.4057	$135.41	$135.40	$135.40
Purchase #6	$93.67	7.286%	$100.4948	$100.49	$100.50	$100.50
Purchase #7	$40.42	4.873%	$42.3897	$42.39	$42.40	$42.40
7 purchase totals =	$697.13		$747.2770	$747.27	$747.30	$747.40