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	$187.81	11.304%	$209.04	$209.04	$209.05	$209.00
Purchase #2	$96.73	6.347%	$102.8695	$102.87	$102.85	$102.90
Purchase #3	$56.96	4.608%	$59.5847	$59.58	$59.60	$59.60
Purchase #4	$46.65	9.171%	$50.9283	$50.93	$50.95	$50.90
Purchase #5	$195.40	9.394%	$213.7559	$213.76	$213.75	$213.80
Purchase #6	$104.92	6.519%	$111.7597	$111.76	$111.75	$111.80
Purchase #7	$152.95	9.282%	$167.1468	$167.15	$167.15	$167.10
7 purchase totals =	$841.42		$915.0849	$915.09	$915.10	$915.10