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	$200.25	10.762%	$221.8009	$221.80	$221.80	$221.80
Purchase #2	$110.28	7.577%	$118.6359	$118.64	$118.65	$118.60
Purchase #3	$89.32	11.181%	$99.3069	$99.31	$99.30	$99.30
Purchase #4	$119.64	7.286%	$128.357	$128.36	$128.35	$128.40
Purchase #5	$216.56	9.808%	$237.8002	$237.80	$237.80	$237.80
Purchase #6	$111.85	12.228%	$125.527	$125.53	$125.55	$125.50
Purchase #7	$157.91	9.242%	$172.504	$172.50	$172.50	$172.50
7 purchase totals =	$1,005.81		$1,103.9319	$1,103.94	$1,103.95	$1,103.90