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	$156.51	12.344%	$175.8296	$175.83	$175.85	$175.80
Purchase #2	$215.51	5.604%	$227.5872	$227.59	$227.60	$227.60
Purchase #3	$212.93	10.199%	$234.6467	$234.65	$234.65	$234.60
Purchase #4	$100.43	13.626%	$114.1146	$114.11	$114.10	$114.10
Purchase #5	$219.91	3.467%	$227.5343	$227.53	$227.55	$227.50
Purchase #6	$81.46	11.513%	$90.8385	$90.84	$90.85	$90.80
Purchase #7	$93.48	7.345%	$100.3461	$100.35	$100.35	$100.30
7 purchase totals =	$1,080.23		$1,170.8970	$1,170.90	$1,170.95	$1,170.70