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	$203.70	4.867%	$213.6141	$213.61	$213.60	$213.60
Purchase #2	$76.77	5.825%	$81.2419	$81.24	$81.25	$81.20
Purchase #3	$54.28	9.841%	$59.6217	$59.62	$59.60	$59.60
Purchase #4	$134.75	7.116%	$144.3388	$144.34	$144.35	$144.30
Purchase #5	$123.74	9.295%	$135.2416	$135.24	$135.25	$135.20
Purchase #6	$94.51	6.343%	$100.5048	$100.50	$100.50	$100.50
Purchase #7	$144.72	4.842%	$151.7273	$151.73	$151.75	$151.70
7 purchase totals =	$832.47		$886.2902	$886.28	$886.30	$886.10