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	$169.86	10.824%	$188.2456	$188.25	$188.25	$188.20
Purchase #2	$52.30	8.487%	$56.7387	$56.74	$56.75	$56.70
Purchase #3	$168.45	9.763%	$184.8958	$184.90	$184.90	$184.90
Purchase #4	$227.45	4.445%	$237.5602	$237.56	$237.55	$237.60
Purchase #5	$62.41	4.506%	$65.2222	$65.22	$65.20	$65.20
Purchase #6	$115.49	3.293%	$119.2931	$119.29	$119.30	$119.30
Purchase #7	$216.60	8.197%	$234.3547	$234.35	$234.35	$234.40
7 purchase totals =	$1,012.56		$1,086.3103	$1,086.31	$1,086.30	$1,086.30