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	$182.85	4.251%	$190.623	$190.62	$190.60	$190.60
Purchase #2	$40.73	10.831%	$45.1415	$45.14	$45.15	$45.10
Purchase #3	$126.32	3.551%	$130.8056	$130.81	$130.80	$130.80
Purchase #4	$210.86	6.250%	$224.0388	$224.04	$224.05	$224.00
Purchase #5	$215.79	12.341%	$242.4206	$242.42	$242.40	$242.40
Purchase #6	$19.91	4.721%	$20.85	$20.85	$20.85	$20.90
Purchase #7	$178.53	4.403%	$186.3907	$186.39	$186.40	$186.40
7 purchase totals =	$974.99		$1,040.2702	$1,040.27	$1,040.25	$1,040.20