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	$70.75	10.319%	$78.0507	$78.05	$78.05	$78.10
Purchase #2	$78.64	12.322%	$88.33	$88.33	$88.35	$88.30
Purchase #3	$153.67	10.855%	$170.3509	$170.35	$170.35	$170.40
Purchase #4	$53.28	6.803%	$56.9046	$56.90	$56.90	$56.90
Purchase #5	$106.96	5.115%	$112.431	$112.43	$112.45	$112.40
Purchase #6	$102.85	9.366%	$112.4829	$112.48	$112.50	$112.50
Purchase #7	$205.80	5.287%	$216.6806	$216.68	$216.70	$216.70
7 purchase totals =	$771.95		$835.2307	$835.22	$835.30	$835.30