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	$243.52	5.359%	$256.5702	$256.57	$256.55	$256.60
Purchase #2	$25.39	9.651%	$27.8404	$27.84	$27.85	$27.80
Purchase #3	$189.66	10.399%	$209.3827	$209.38	$209.40	$209.40
Purchase #4	$107.34	5.136%	$112.853	$112.85	$112.85	$112.90
Purchase #5	$243.88	10.467%	$269.4069	$269.41	$269.40	$269.40
Purchase #6	$53.41	12.772%	$60.2315	$60.23	$60.25	$60.20
Purchase #7	$121.33	4.868%	$127.2363	$127.24	$127.25	$127.20
7 purchase totals =	$984.53		$1,063.5210	$1,063.52	$1,063.55	$1,063.50