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	$105.36	5.281%	$110.9241	$110.92	$110.90	$110.90
Purchase #2	$40.65	11.809%	$45.4504	$45.45	$45.45	$45.50
Purchase #3	$41.71	3.843%	$43.3129	$43.31	$43.30	$43.30
Purchase #4	$32.31	4.352%	$33.7161	$33.72	$33.70	$33.70
Purchase #5	$107.88	6.231%	$114.602	$114.60	$114.60	$114.60
Purchase #6	$97.62	3.354%	$100.8942	$100.89	$100.90	$100.90
Purchase #7	$6.46	4.720%	$6.7649	$6.76	$6.75	$6.80
7 purchase totals =	$431.99		$455.6646	$455.65	$455.60	$455.70