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	$185.71	5.826%	$196.5295	$196.53	$196.55	$196.50
Purchase #2	$215.41	4.579%	$225.2736	$225.27	$225.25	$225.30
Purchase #3	$221.51	6.872%	$236.7322	$236.73	$236.75	$236.70
Purchase #4	$173.32	3.810%	$179.9235	$179.92	$179.90	$179.90
Purchase #5	$69.31	10.300%	$76.4489	$76.45	$76.45	$76.40
Purchase #6	$157.85	10.811%	$174.9152	$174.92	$174.90	$174.90
Purchase #7	$82.73	11.300%	$92.0785	$92.08	$92.10	$92.10
7 purchase totals =	$1,105.84		$1,181.9014	$1,181.90	$1,181.90	$1,181.80