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	$45.76	3.305%	$47.2724	$47.27	$47.25	$47.30
Purchase #2	$147.65	6.309%	$156.9652	$156.97	$156.95	$157.00
Purchase #3	$7.46	11.563%	$8.3226	$8.32	$8.30	$8.30
Purchase #4	$13.35	7.345%	$14.3306	$14.33	$14.35	$14.30
Purchase #5	$49.35	9.845%	$54.2085	$54.21	$54.20	$54.20
Purchase #6	$119.81	7.103%	$128.3201	$128.32	$128.30	$128.30
Purchase #7	$54.31	9.769%	$59.6155	$59.62	$59.60	$59.60
7 purchase totals =	$437.69		$469.0349	$469.04	$468.95	$469.00