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	$228.56	4.527%	$238.9069	$238.91	$238.90	$238.90
Purchase #2	$229.45	4.289%	$239.2911	$239.29	$239.30	$239.30
Purchase #3	$85.69	4.581%	$89.6155	$89.62	$89.60	$89.60
Purchase #4	$120.71	7.298%	$129.5194	$129.52	$129.50	$129.50
Purchase #5	$227.29	12.436%	$255.5558	$255.56	$255.55	$255.60
Purchase #6	$102.98	4.367%	$107.4771	$107.48	$107.50	$107.50
Purchase #7	$248.55	13.796%	$282.84	$282.84	$282.85	$282.80
7 purchase totals =	$1,243.23		$1,343.2058	$1,343.22	$1,343.20	$1,343.20