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	$156.46	3.542%	$162.0018	$162.00	$162.00	$162.00
Purchase #2	$88.95	7.186%	$95.3419	$95.34	$95.35	$95.30
Purchase #3	$205.41	5.343%	$216.3851	$216.39	$216.40	$216.40
Purchase #4	$223.34	3.839%	$231.914	$231.91	$231.90	$231.90
Purchase #5	$40.25	6.285%	$42.7797	$42.78	$42.80	$42.80
Purchase #6	$34.79	4.439%	$36.3343	$36.33	$36.35	$36.30
Purchase #7	$67.29	4.869%	$70.5664	$70.57	$70.55	$70.60
7 purchase totals =	$816.49		$855.3232	$855.32	$855.35	$855.30