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	$104.37	4.709%	$109.2848	$109.28	$109.30	$109.30
Purchase #2	$154.52	9.583%	$169.3277	$169.33	$169.35	$169.30
Purchase #3	$132.52	11.656%	$147.9665	$147.97	$147.95	$148.00
Purchase #4	$92.29	12.579%	$103.8992	$103.90	$103.90	$103.90
Purchase #5	$218.83	6.502%	$233.0583	$233.06	$233.05	$233.10
Purchase #6	$213.81	10.152%	$235.516	$235.52	$235.50	$235.50
Purchase #7	$238.44	4.540%	$249.2652	$249.27	$249.25	$249.30
7 purchase totals =	$1,154.78		$1,248.3177	$1,248.33	$1,248.30	$1,248.40