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	$69.47	4.743%	$72.765	$72.77	$72.75	$72.80
Purchase #2	$85.65	8.324%	$92.7795	$92.78	$92.80	$92.80
Purchase #3	$227.72	8.871%	$247.921	$247.92	$247.90	$247.90
Purchase #4	$31.67	13.242%	$35.8637	$35.86	$35.85	$35.90
Purchase #5	$228.37	7.570%	$245.6576	$245.66	$245.65	$245.70
Purchase #6	$53.28	4.368%	$55.6073	$55.61	$55.60	$55.60
Purchase #7	$88.46	9.427%	$96.7991	$96.80	$96.80	$96.80
7 purchase totals =	$784.62		$847.3932	$847.40	$847.35	$847.50