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	$144.28	12.813%	$162.7666	$162.77	$162.75	$162.80
Purchase #2	$28.33	5.385%	$29.8556	$29.86	$29.85	$29.90
Purchase #3	$82.69	6.230%	$87.8416	$87.84	$87.85	$87.80
Purchase #4	$144.27	5.224%	$151.8067	$151.81	$151.80	$151.80
Purchase #5	$23.37	9.149%	$25.5081	$25.51	$25.50	$25.50
Purchase #6	$29.32	10.616%	$32.4326	$32.43	$32.45	$32.40
Purchase #7	$179.61	6.637%	$191.5307	$191.53	$191.55	$191.50
7 purchase totals =	$631.87		$681.7419	$681.75	$681.75	$681.70