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	$129.61	11.442%	$144.44	$144.44	$144.45	$144.40
Purchase #2	$206.71	8.167%	$223.592	$223.59	$223.60	$223.60
Purchase #3	$199.69	8.210%	$216.0845	$216.08	$216.10	$216.10
Purchase #4	$234.83	4.868%	$246.2615	$246.26	$246.25	$246.30
Purchase #5	$91.88	8.287%	$99.4941	$99.49	$99.50	$99.50
Purchase #6	$211.36	3.419%	$218.5864	$218.59	$218.60	$218.60
Purchase #7	$137.74	9.740%	$151.1559	$151.16	$151.15	$151.20
7 purchase totals =	$1,211.82		$1,299.6144	$1,299.61	$1,299.65	$1,299.70