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	$110.65	11.736%	$123.6359	$123.64	$123.65	$123.60
Purchase #2	$163.33	5.516%	$172.3393	$172.34	$172.35	$172.30
Purchase #3	$221.56	6.557%	$236.0877	$236.09	$236.10	$236.10
Purchase #4	$202.64	9.369%	$221.6253	$221.63	$221.65	$221.60
Purchase #5	$72.78	11.429%	$81.098	$81.10	$81.10	$81.10
Purchase #6	$35.83	12.704%	$40.3818	$40.38	$40.40	$40.40
Purchase #7	$83.68	9.797%	$91.8781	$91.88	$91.90	$91.90
7 purchase totals =	$890.47		$967.0461	$967.06	$967.15	$967.00