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	$42.74	9.336%	$46.7302	$46.73	$46.75	$46.70
Purchase #2	$172.93	9.531%	$189.412	$189.41	$189.40	$189.40
Purchase #3	$43.49	8.224%	$47.0666	$47.07	$47.05	$47.10
Purchase #4	$222.93	7.153%	$238.8762	$238.88	$238.90	$238.90
Purchase #5	$236.72	5.669%	$250.1397	$250.14	$250.15	$250.10
Purchase #6	$162.27	8.726%	$176.4297	$176.43	$176.45	$176.40
Purchase #7	$108.96	3.524%	$112.7998	$112.80	$112.80	$112.80
7 purchase totals =	$990.04		$1,061.4542	$1,061.46	$1,061.50	$1,061.40