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	$31.33	13.426%	$35.5364	$35.54	$35.55	$35.50
Purchase #2	$196.36	4.828%	$205.8403	$205.84	$205.85	$205.80
Purchase #3	$67.61	4.781%	$70.8424	$70.84	$70.85	$70.80
Purchase #4	$191.89	11.843%	$214.6155	$214.62	$214.60	$214.60
Purchase #5	$148.76	13.114%	$168.2684	$168.27	$168.25	$168.30
Purchase #6	$51.32	10.774%	$56.8492	$56.85	$56.85	$56.80
Purchase #7	$146.65	13.618%	$166.6208	$166.62	$166.60	$166.60
7 purchase totals =	$833.92		$918.5730	$918.58	$918.55	$918.40