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	$203.38	8.389%	$220.4415	$220.44	$220.45	$220.40
Purchase #2	$59.51	9.663%	$65.2605	$65.26	$65.25	$65.30
Purchase #3	$220.44	9.737%	$241.9042	$241.90	$241.90	$241.90
Purchase #4	$175.84	7.711%	$189.399	$189.40	$189.40	$189.40
Purchase #5	$167.78	10.524%	$185.4372	$185.44	$185.45	$185.40
Purchase #6	$216.27	3.794%	$224.4753	$224.48	$224.50	$224.50
Purchase #7	$80.73	11.470%	$89.9897	$89.99	$90.00	$90.00
7 purchase totals =	$1,123.95		$1,216.9074	$1,216.91	$1,216.95	$1,216.90