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	$69.38	11.505%	$77.3622	$77.36	$77.35	$77.40
Purchase #2	$213.91	4.367%	$223.2514	$223.25	$223.25	$223.30
Purchase #3	$245.50	13.848%	$279.4968	$279.50	$279.50	$279.50
Purchase #4	$206.46	7.488%	$221.9197	$221.92	$221.90	$221.90
Purchase #5	$195.26	13.578%	$221.7724	$221.77	$221.75	$221.80
Purchase #6	$56.46	5.700%	$59.6782	$59.68	$59.70	$59.70
Purchase #7	$83.36	3.134%	$85.9725	$85.97	$85.95	$86.00
7 purchase totals =	$1,070.33		$1,169.4532	$1,169.45	$1,169.40	$1,169.60