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	$193.50	3.304%	$199.8932	$199.89	$199.90	$199.90
Purchase #2	$40.88	11.789%	$45.6993	$45.70	$45.70	$45.70
Purchase #3	$177.38	4.837%	$185.9599	$185.96	$185.95	$186.00
Purchase #4	$35.61	12.444%	$40.0413	$40.04	$40.05	$40.00
Purchase #5	$179.92	3.461%	$186.147	$186.15	$186.15	$186.10
Purchase #6	$217.72	11.254%	$242.2222	$242.22	$242.20	$242.20
Purchase #7	$187.31	5.137%	$196.9321	$196.93	$196.95	$196.90
7 purchase totals =	$1,032.32		$1,096.8950	$1,096.89	$1,096.90	$1,096.80