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	$61.94	13.198%	$70.1148	$70.11	$70.10	$70.10
Purchase #2	$208.77	6.383%	$222.0958	$222.10	$222.10	$222.10
Purchase #3	$108.45	3.454%	$112.1959	$112.20	$112.20	$112.20
Purchase #4	$96.53	6.514%	$102.818	$102.82	$102.80	$102.80
Purchase #5	$98.35	13.825%	$111.9469	$111.95	$111.95	$111.90
Purchase #6	$220.38	7.750%	$237.4595	$237.46	$237.45	$237.50
Purchase #7	$212.61	11.190%	$236.4011	$236.40	$236.40	$236.40
7 purchase totals =	$1,007.03		$1,093.0320	$1,093.04	$1,093.00	$1,093.00