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	$84.27	9.293%	$92.1012	$92.10	$92.10	$92.10
Purchase #2	$18.79	9.201%	$20.5189	$20.52	$20.50	$20.50
Purchase #3	$64.64	11.599%	$72.1376	$72.14	$72.15	$72.10
Purchase #4	$240.67	11.288%	$267.8368	$267.84	$267.85	$267.80
Purchase #5	$54.64	9.699%	$59.9395	$59.94	$59.95	$59.90
Purchase #6	$225.59	5.750%	$238.5614	$238.56	$238.55	$238.60
Purchase #7	$141.31	8.212%	$152.9144	$152.91	$152.90	$152.90
7 purchase totals =	$829.91		$904.0098	$904.01	$904.00	$903.90