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	$143.94	4.661%	$150.649	$150.65	$150.65	$150.60
Purchase #2	$145.34	3.527%	$150.4661	$150.47	$150.45	$150.50
Purchase #3	$245.57	6.708%	$262.0428	$262.04	$262.05	$262.00
Purchase #4	$6.55	7.698%	$7.0542	$7.05	$7.05	$7.10
Purchase #5	$109.49	11.356%	$121.9237	$121.92	$121.90	$121.90
Purchase #6	$33.52	5.233%	$35.2741	$35.27	$35.25	$35.30
Purchase #7	$76.25	3.573%	$78.9744	$78.97	$78.95	$79.00
7 purchase totals =	$760.66		$806.3843	$806.37	$806.30	$806.40