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	$186.66	7.533%	$200.7211	$200.72	$200.70	$200.70
Purchase #2	$191.76	9.671%	$210.3051	$210.31	$210.30	$210.30
Purchase #3	$78.92	7.471%	$84.8161	$84.82	$84.80	$84.80
Purchase #4	$18.61	8.151%	$20.1269	$20.13	$20.15	$20.10
Purchase #5	$190.55	5.176%	$200.4129	$200.41	$200.40	$200.40
Purchase #6	$247.33	10.750%	$273.918	$273.92	$273.90	$273.90
Purchase #7	$60.37	11.370%	$67.2341	$67.23	$67.25	$67.20
7 purchase totals =	$974.20		$1,057.5342	$1,057.54	$1,057.50	$1,057.40