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	$73.99	6.567%	$78.8489	$78.85	$78.85	$78.80
Purchase #2	$198.31	5.568%	$209.3519	$209.35	$209.35	$209.40
Purchase #3	$158.95	13.550%	$180.4877	$180.49	$180.50	$180.50
Purchase #4	$233.25	13.543%	$264.839	$264.84	$264.85	$264.80
Purchase #5	$12.82	8.346%	$13.89	$13.89	$13.90	$13.90
Purchase #6	$96.65	7.552%	$103.949	$103.95	$103.95	$103.90
Purchase #7	$68.33	12.598%	$76.9382	$76.94	$76.95	$76.90
7 purchase totals =	$842.30		$928.3047	$928.31	$928.35	$928.20