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	$237.45	3.351%	$245.4069	$245.41	$245.40	$245.40
Purchase #2	$43.89	10.123%	$48.333	$48.33	$48.35	$48.30
Purchase #3	$103.35	3.540%	$107.0086	$107.01	$107.00	$107.00
Purchase #4	$57.39	4.788%	$60.1378	$60.14	$60.15	$60.10
Purchase #5	$148.35	5.770%	$156.9098	$156.91	$156.90	$156.90
Purchase #6	$72.51	6.765%	$77.4153	$77.42	$77.40	$77.40
Purchase #7	$73.50	7.129%	$78.7398	$78.74	$78.75	$78.70
7 purchase totals =	$736.44		$773.9512	$773.96	$773.95	$773.80