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	$114.93	11.159%	$127.755	$127.76	$127.75	$127.80
Purchase #2	$237.28	5.240%	$249.7135	$249.71	$249.70	$249.70
Purchase #3	$158.73	10.181%	$174.8903	$174.89	$174.90	$174.90
Purchase #4	$46.97	3.596%	$48.659	$48.66	$48.65	$48.70
Purchase #5	$180.40	7.309%	$193.5854	$193.59	$193.60	$193.60
Purchase #6	$90.56	10.285%	$99.8741	$99.87	$99.85	$99.90
Purchase #7	$109.69	11.735%	$122.5621	$122.56	$122.55	$122.60
7 purchase totals =	$938.56		$1,017.0394	$1,017.04	$1,017.00	$1,017.20