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	$159.50	6.185%	$169.3651	$169.37	$169.35	$169.40
Purchase #2	$218.27	11.148%	$242.6027	$242.60	$242.60	$242.60
Purchase #3	$159.70	9.205%	$174.4004	$174.40	$174.40	$174.40
Purchase #4	$127.99	10.630%	$141.5953	$141.60	$141.60	$141.60
Purchase #5	$184.59	12.751%	$208.1271	$208.13	$208.15	$208.10
Purchase #6	$121.46	8.276%	$131.512	$131.51	$131.50	$131.50
Purchase #7	$173.74	6.735%	$185.4414	$185.44	$185.45	$185.40
7 purchase totals =	$1,145.25		$1,253.0440	$1,253.05	$1,253.05	$1,253.00