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	$66.44	7.774%	$71.605	$71.61	$71.60	$71.60
Purchase #2	$51.45	10.351%	$56.7756	$56.78	$56.80	$56.80
Purchase #3	$94.66	11.236%	$105.296	$105.30	$105.30	$105.30
Purchase #4	$175.48	9.209%	$191.64	$191.64	$191.65	$191.60
Purchase #5	$16.72	12.689%	$18.8416	$18.84	$18.85	$18.80
Purchase #6	$169.47	3.496%	$175.3947	$175.39	$175.40	$175.40
Purchase #7	$53.46	8.327%	$57.9116	$57.91	$57.90	$57.90
7 purchase totals =	$627.68		$677.4645	$677.47	$677.50	$677.40