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	$134.89	5.665%	$142.5315	$142.53	$142.55	$142.50
Purchase #2	$92.80	13.519%	$105.3456	$105.35	$105.35	$105.30
Purchase #3	$56.81	4.425%	$59.3238	$59.32	$59.30	$59.30
Purchase #4	$121.75	5.676%	$128.6605	$128.66	$128.65	$128.70
Purchase #5	$196.53	13.680%	$223.4153	$223.42	$223.40	$223.40
Purchase #6	$235.75	11.560%	$263.0027	$263.00	$263.00	$263.00
Purchase #7	$155.79	7.404%	$167.3247	$167.32	$167.30	$167.30
7 purchase totals =	$994.32		$1,089.6041	$1,089.60	$1,089.55	$1,089.50