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	$100.33	4.488%	$104.8328	$104.83	$104.85	$104.80
Purchase #2	$131.31	8.661%	$142.6828	$142.68	$142.70	$142.70
Purchase #3	$111.81	13.759%	$127.1939	$127.19	$127.20	$127.20
Purchase #4	$87.40	10.282%	$96.3865	$96.39	$96.40	$96.40
Purchase #5	$210.97	11.556%	$235.3497	$235.35	$235.35	$235.30
Purchase #6	$167.53	6.516%	$178.4463	$178.45	$178.45	$178.40
Purchase #7	$115.75	13.591%	$131.4816	$131.48	$131.50	$131.50
7 purchase totals =	$925.10		$1,016.3736	$1,016.37	$1,016.45	$1,016.30