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	$133.66	8.315%	$144.7738	$144.77	$144.75	$144.80
Purchase #2	$147.78	11.484%	$164.7511	$164.75	$164.75	$164.80
Purchase #3	$133.68	13.311%	$151.4741	$151.47	$151.45	$151.50
Purchase #4	$133.92	7.741%	$144.2867	$144.29	$144.30	$144.30
Purchase #5	$242.59	9.335%	$265.2358	$265.24	$265.25	$265.20
Purchase #6	$35.59	12.807%	$40.148	$40.15	$40.15	$40.10
Purchase #7	$232.73	13.442%	$264.0136	$264.01	$264.00	$264.00
7 purchase totals =	$1,059.95		$1,174.6831	$1,174.68	$1,174.65	$1,174.70