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	$205.65	8.697%	$223.5354	$223.54	$223.55	$223.50
Purchase #2	$236.48	7.778%	$254.8734	$254.87	$254.85	$254.90
Purchase #3	$99.29	11.262%	$110.472	$110.47	$110.45	$110.50
Purchase #4	$139.45	11.851%	$155.9762	$155.98	$156.00	$156.00
Purchase #5	$197.71	8.439%	$214.3947	$214.39	$214.40	$214.40
Purchase #6	$125.38	4.153%	$130.587	$130.59	$130.60	$130.60
Purchase #7	$86.95	4.216%	$90.6158	$90.62	$90.60	$90.60
7 purchase totals =	$1,090.91		$1,180.4545	$1,180.46	$1,180.45	$1,180.50