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	$163.34	7.639%	$175.8175	$175.82	$175.80	$175.80
Purchase #2	$247.45	7.720%	$266.5531	$266.55	$266.55	$266.60
Purchase #3	$122.60	6.385%	$130.428	$130.43	$130.45	$130.40
Purchase #4	$239.39	11.574%	$267.097	$267.10	$267.10	$267.10
Purchase #5	$28.93	10.502%	$31.9682	$31.97	$31.95	$32.00
Purchase #6	$114.73	11.209%	$127.5901	$127.59	$127.60	$127.60
Purchase #7	$187.79	4.850%	$196.8978	$196.90	$196.90	$196.90
7 purchase totals =	$1,104.23		$1,196.3517	$1,196.36	$1,196.35	$1,196.40