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	$135.93	5.682%	$143.6535	$143.65	$143.65	$143.70
Purchase #2	$187.91	11.439%	$209.405	$209.41	$209.40	$209.40
Purchase #3	$90.98	9.711%	$99.8151	$99.82	$99.80	$99.80
Purchase #4	$210.94	9.452%	$230.878	$230.88	$230.90	$230.90
Purchase #5	$218.83	10.722%	$242.293	$242.29	$242.30	$242.30
Purchase #6	$93.78	7.168%	$100.5022	$100.50	$100.50	$100.50
Purchase #7	$141.41	6.710%	$150.8986	$150.90	$150.90	$150.90
7 purchase totals =	$1,079.78		$1,177.4454	$1,177.45	$1,177.45	$1,177.50