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	$81.98	7.755%	$88.3375	$88.34	$88.35	$88.30
Purchase #2	$27.82	13.471%	$31.5676	$31.57	$31.55	$31.60
Purchase #3	$136.92	3.219%	$141.3275	$141.33	$141.35	$141.30
Purchase #4	$128.34	11.738%	$143.4045	$143.40	$143.40	$143.40
Purchase #5	$107.29	4.606%	$112.2318	$112.23	$112.25	$112.20
Purchase #6	$141.43	3.614%	$146.5413	$146.54	$146.55	$146.50
Purchase #7	$231.78	4.742%	$242.771	$242.77	$242.75	$242.80
7 purchase totals =	$855.56		$906.1812	$906.18	$906.20	$906.10