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	$26.30	11.179%	$29.2401	$29.24	$29.25	$29.20
Purchase #2	$43.96	5.179%	$46.2367	$46.24	$46.25	$46.20
Purchase #3	$65.48	4.468%	$68.4056	$68.41	$68.40	$68.40
Purchase #4	$178.94	10.736%	$198.151	$198.15	$198.15	$198.20
Purchase #5	$145.29	9.787%	$159.5095	$159.51	$159.50	$159.50
Purchase #6	$160.60	7.391%	$172.4699	$172.47	$172.45	$172.50
Purchase #7	$55.83	7.244%	$59.8743	$59.87	$59.85	$59.90
7 purchase totals =	$676.40		$733.8871	$733.89	$733.85	$733.90