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	$213.68	10.128%	$235.3215	$235.32	$235.30	$235.30
Purchase #2	$90.57	6.794%	$96.7233	$96.72	$96.70	$96.70
Purchase #3	$179.67	6.840%	$191.9594	$191.96	$191.95	$192.00
Purchase #4	$144.34	3.582%	$149.5103	$149.51	$149.50	$149.50
Purchase #5	$104.93	11.869%	$117.3841	$117.38	$117.40	$117.40
Purchase #6	$144.77	9.181%	$158.0613	$158.06	$158.05	$158.10
Purchase #7	$102.90	9.560%	$112.7372	$112.74	$112.75	$112.70
7 purchase totals =	$980.86		$1,061.6971	$1,061.69	$1,061.65	$1,061.70