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	$169.77	11.311%	$188.9727	$188.97	$188.95	$189.00
Purchase #2	$65.28	4.748%	$68.3795	$68.38	$68.40	$68.40
Purchase #3	$87.76	13.128%	$99.2811	$99.28	$99.30	$99.30
Purchase #4	$19.97	12.367%	$22.4397	$22.44	$22.45	$22.40
Purchase #5	$31.66	11.449%	$35.2848	$35.28	$35.30	$35.30
Purchase #6	$71.43	9.849%	$78.4651	$78.47	$78.45	$78.50
Purchase #7	$175.67	11.443%	$195.7719	$195.77	$195.75	$195.80
7 purchase totals =	$621.54		$688.5948	$688.59	$688.60	$688.70