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	$65.73	9.585%	$72.0302	$72.03	$72.05	$72.00
Purchase #2	$219.91	6.296%	$233.7555	$233.76	$233.75	$233.80
Purchase #3	$16.33	11.786%	$18.2547	$18.25	$18.25	$18.30
Purchase #4	$49.27	12.786%	$55.5697	$55.57	$55.55	$55.60
Purchase #5	$241.84	4.733%	$253.2863	$253.29	$253.30	$253.30
Purchase #6	$156.96	6.221%	$166.7245	$166.72	$166.70	$166.70
Purchase #7	$167.75	4.790%	$175.7852	$175.79	$175.80	$175.80
7 purchase totals =	$917.79		$975.4061	$975.41	$975.40	$975.50