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	$80.86	9.126%	$88.2393	$88.24	$88.25	$88.20
Purchase #2	$73.37	12.815%	$82.7724	$82.77	$82.75	$82.80
Purchase #3	$209.64	9.448%	$229.4468	$229.45	$229.45	$229.40
Purchase #4	$101.55	3.615%	$105.221	$105.22	$105.20	$105.20
Purchase #5	$180.38	8.770%	$196.1993	$196.20	$196.20	$196.20
Purchase #6	$101.45	11.322%	$112.9362	$112.94	$112.95	$112.90
Purchase #7	$189.97	7.269%	$203.7789	$203.78	$203.80	$203.80
7 purchase totals =	$937.22		$1,018.5939	$1,018.60	$1,018.60	$1,018.50