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	$45.28	4.255%	$47.2067	$47.21	$47.20	$47.20
Purchase #2	$31.72	10.350%	$35.003	$35.00	$35.00	$35.00
Purchase #3	$68.49	11.642%	$76.4636	$76.46	$76.45	$76.50
Purchase #4	$55.45	11.387%	$61.7641	$61.76	$61.75	$61.80
Purchase #5	$130.66	6.843%	$139.6011	$139.60	$139.60	$139.60
Purchase #6	$178.71	3.255%	$184.527	$184.53	$184.55	$184.50
Purchase #7	$99.69	9.638%	$109.2981	$109.30	$109.30	$109.30
7 purchase totals =	$610.00		$653.8636	$653.86	$653.85	$653.90