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	$162.62	11.548%	$181.3994	$181.40	$181.40	$181.40
Purchase #2	$141.45	3.339%	$146.173	$146.17	$146.15	$146.20
Purchase #3	$100.43	6.265%	$106.7219	$106.72	$106.70	$106.70
Purchase #4	$184.89	13.807%	$210.4178	$210.42	$210.40	$210.40
Purchase #5	$236.59	13.495%	$268.5178	$268.52	$268.50	$268.50
Purchase #6	$151.25	13.844%	$172.1891	$172.19	$172.20	$172.20
Purchase #7	$250.72	9.873%	$275.4736	$275.47	$275.45	$275.50
7 purchase totals =	$1,227.95		$1,360.8926	$1,360.89	$1,360.80	$1,360.90