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	$175.93	11.757%	$196.6141	$196.61	$196.60	$196.60
Purchase #2	$89.56	11.751%	$100.0842	$100.08	$100.10	$100.10
Purchase #3	$47.86	10.403%	$52.8389	$52.84	$52.85	$52.80
Purchase #4	$93.84	10.262%	$103.4699	$103.47	$103.45	$103.50
Purchase #5	$202.56	6.813%	$216.3604	$216.36	$216.35	$216.40
Purchase #6	$240.56	8.345%	$260.6347	$260.63	$260.65	$260.60
Purchase #7	$191.77	13.741%	$218.1211	$218.12	$218.10	$218.10
7 purchase totals =	$1,042.08		$1,148.1233	$1,148.11	$1,148.10	$1,148.10