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	$184.44	3.342%	$190.604	$190.60	$190.60	$190.60
Purchase #2	$78.26	9.432%	$85.6415	$85.64	$85.65	$85.60
Purchase #3	$165.38	11.854%	$184.9841	$184.98	$185.00	$185.00
Purchase #4	$47.78	9.385%	$52.2642	$52.26	$52.25	$52.30
Purchase #5	$189.91	7.131%	$203.4525	$203.45	$203.45	$203.50
Purchase #6	$191.45	11.676%	$213.8037	$213.80	$213.80	$213.80
Purchase #7	$173.82	13.210%	$196.7816	$196.78	$196.80	$196.80
7 purchase totals =	$1,031.04		$1,127.5316	$1,127.51	$1,127.55	$1,127.60