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	$101.86	7.764%	$109.7684	$109.77	$109.75	$109.80
Purchase #2	$119.49	11.369%	$133.0748	$133.07	$133.05	$133.10
Purchase #3	$105.78	5.337%	$111.4255	$111.43	$111.45	$111.40
Purchase #4	$92.31	13.806%	$105.0543	$105.05	$105.05	$105.10
Purchase #5	$89.79	9.788%	$98.5786	$98.58	$98.60	$98.60
Purchase #6	$92.41	4.630%	$96.6886	$96.69	$96.70	$96.70
Purchase #7	$183.65	5.569%	$193.8775	$193.88	$193.90	$193.90
7 purchase totals =	$785.29		$848.4677	$848.47	$848.50	$848.60