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	$171.48	8.430%	$185.9358	$185.94	$185.95	$185.90
Purchase #2	$231.28	7.667%	$249.0122	$249.01	$249.00	$249.00
Purchase #3	$142.75	11.831%	$159.6388	$159.64	$159.65	$159.60
Purchase #4	$16.94	11.394%	$18.8701	$18.87	$18.85	$18.90
Purchase #5	$5.52	11.212%	$6.1389	$6.14	$6.15	$6.10
Purchase #6	$113.73	8.739%	$123.6689	$123.67	$123.65	$123.70
Purchase #7	$234.39	11.802%	$262.0527	$262.05	$262.05	$262.10
7 purchase totals =	$916.09		$1,005.3174	$1,005.32	$1,005.30	$1,005.30