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	$248.79	10.831%	$275.7364	$275.74	$275.75	$275.70
Purchase #2	$191.46	10.228%	$211.0425	$211.04	$211.05	$211.00
Purchase #3	$94.91	13.259%	$107.4941	$107.49	$107.50	$107.50
Purchase #4	$117.96	7.744%	$127.0948	$127.09	$127.10	$127.10
Purchase #5	$45.85	7.767%	$49.4112	$49.41	$49.40	$49.40
Purchase #6	$139.36	10.616%	$154.1545	$154.15	$154.15	$154.20
Purchase #7	$88.54	6.509%	$94.3031	$94.30	$94.30	$94.30
7 purchase totals =	$926.87		$1,019.2366	$1,019.22	$1,019.25	$1,019.20