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	$160.60	7.817%	$173.1541	$173.15	$173.15	$173.20
Purchase #2	$222.44	8.451%	$241.2384	$241.24	$241.25	$241.20
Purchase #3	$62.59	12.479%	$70.4006	$70.40	$70.40	$70.40
Purchase #4	$211.90	7.755%	$228.3328	$228.33	$228.35	$228.30
Purchase #5	$54.56	4.210%	$56.857	$56.86	$56.85	$56.90
Purchase #6	$152.39	8.587%	$165.4757	$165.48	$165.50	$165.50
Purchase #7	$189.86	12.499%	$213.5906	$213.59	$213.60	$213.60
7 purchase totals =	$1,054.34		$1,149.0492	$1,149.05	$1,149.10	$1,149.10