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	$228.51	3.416%	$236.3159	$236.32	$236.30	$236.30
Purchase #2	$179.33	9.782%	$196.8721	$196.87	$196.85	$196.90
Purchase #3	$161.42	4.585%	$168.8211	$168.82	$168.80	$168.80
Purchase #4	$7.72	6.843%	$8.2483	$8.25	$8.25	$8.20
Purchase #5	$93.40	11.254%	$103.9112	$103.91	$103.90	$103.90
Purchase #6	$202.97	5.590%	$214.316	$214.32	$214.30	$214.30
Purchase #7	$90.80	12.192%	$101.8703	$101.87	$101.85	$101.90
7 purchase totals =	$964.15		$1,030.3549	$1,030.36	$1,030.25	$1,030.30