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	$176.81	4.630%	$184.9963	$185.00	$185.00	$185.00
Purchase #2	$86.29	3.716%	$89.4965	$89.50	$89.50	$89.50
Purchase #3	$111.82	10.231%	$123.2603	$123.26	$123.25	$123.30
Purchase #4	$85.57	8.562%	$92.8965	$92.90	$92.90	$92.90
Purchase #5	$35.86	13.563%	$40.7237	$40.72	$40.70	$40.70
Purchase #6	$140.99	4.518%	$147.3599	$147.36	$147.35	$147.40
Purchase #7	$161.88	10.592%	$179.0263	$179.03	$179.05	$179.00
7 purchase totals =	$799.22		$857.7595	$857.77	$857.75	$857.80