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	$88.46	11.407%	$98.5506	$98.55	$98.55	$98.60
Purchase #2	$245.40	4.502%	$256.4479	$256.45	$256.45	$256.40
Purchase #3	$16.87	6.495%	$17.9657	$17.97	$17.95	$18.00
Purchase #4	$111.53	3.587%	$115.5306	$115.53	$115.55	$115.50
Purchase #5	$31.48	13.162%	$35.6234	$35.62	$35.60	$35.60
Purchase #6	$242.39	9.764%	$266.057	$266.06	$266.05	$266.10
Purchase #7	$205.62	8.123%	$222.3225	$222.32	$222.30	$222.30
7 purchase totals =	$941.75		$1,012.4977	$1,012.50	$1,012.45	$1,012.50