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	$228.94	3.741%	$237.5046	$237.50	$237.50	$237.50
Purchase #2	$72.41	13.801%	$82.4033	$82.40	$82.40	$82.40
Purchase #3	$196.52	7.108%	$210.4886	$210.49	$210.50	$210.50
Purchase #4	$250.49	5.403%	$264.024	$264.02	$264.00	$264.00
Purchase #5	$84.84	13.847%	$96.5878	$96.59	$96.60	$96.60
Purchase #6	$22.55	12.735%	$25.4217	$25.42	$25.40	$25.40
Purchase #7	$178.61	9.189%	$195.0225	$195.02	$195.00	$195.00
7 purchase totals =	$1,034.36		$1,111.4525	$1,111.44	$1,111.40	$1,111.40