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	$186.39	13.722%	$211.9664	$211.97	$211.95	$212.00
Purchase #2	$50.48	4.871%	$52.9389	$52.94	$52.95	$52.90
Purchase #3	$119.91	7.144%	$128.4764	$128.48	$128.50	$128.50
Purchase #4	$97.73	11.374%	$108.8458	$108.85	$108.85	$108.80
Purchase #5	$76.51	7.759%	$82.4464	$82.45	$82.45	$82.40
Purchase #6	$28.25	4.726%	$29.5851	$29.59	$29.60	$29.60
Purchase #7	$72.62	7.815%	$78.2953	$78.30	$78.30	$78.30
7 purchase totals =	$631.89		$692.5543	$692.58	$692.60	$692.50