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	$78.25	6.846%	$83.607	$83.61	$83.60	$83.60
Purchase #2	$77.35	4.211%	$80.6072	$80.61	$80.60	$80.60
Purchase #3	$204.98	8.172%	$221.731	$221.73	$221.75	$221.70
Purchase #4	$77.30	4.650%	$80.8945	$80.89	$80.90	$80.90
Purchase #5	$5.72	3.463%	$5.9181	$5.92	$5.90	$5.90
Purchase #6	$197.61	4.504%	$206.5104	$206.51	$206.50	$206.50
Purchase #7	$240.55	9.585%	$263.6067	$263.61	$263.60	$263.60
7 purchase totals =	$881.76		$942.8749	$942.88	$942.85	$942.80