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	$80.43	8.751%	$87.4684	$87.47	$87.45	$87.50
Purchase #2	$156.63	11.475%	$174.6033	$174.60	$174.60	$174.60
Purchase #3	$73.85	11.224%	$82.1389	$82.14	$82.15	$82.10
Purchase #4	$127.41	9.484%	$139.4936	$139.49	$139.50	$139.50
Purchase #5	$209.73	5.769%	$221.8293	$221.83	$221.85	$221.80
Purchase #6	$170.66	6.779%	$182.229	$182.23	$182.25	$182.20
Purchase #7	$190.80	3.129%	$196.7701	$196.77	$196.75	$196.80
7 purchase totals =	$1,009.51		$1,084.5326	$1,084.53	$1,084.55	$1,084.50