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	$148.99	11.792%	$166.5589	$166.56	$166.55	$166.60
Purchase #2	$61.47	6.630%	$65.5455	$65.55	$65.55	$65.50
Purchase #3	$196.33	13.383%	$222.6048	$222.60	$222.60	$222.60
Purchase #4	$185.74	12.323%	$208.6287	$208.63	$208.65	$208.60
Purchase #5	$94.84	9.678%	$104.0186	$104.02	$104.00	$104.00
Purchase #6	$168.26	13.312%	$190.6588	$190.66	$190.65	$190.70
Purchase #7	$93.46	13.591%	$106.1621	$106.16	$106.15	$106.20
7 purchase totals =	$949.09		$1,064.1774	$1,064.18	$1,064.15	$1,064.20