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	$66.37	10.317%	$73.2174	$73.22	$73.20	$73.20
Purchase #2	$69.94	11.687%	$78.1139	$78.11	$78.10	$78.10
Purchase #3	$71.79	9.215%	$78.4054	$78.41	$78.40	$78.40
Purchase #4	$245.58	9.479%	$268.8585	$268.86	$268.85	$268.90
Purchase #5	$64.37	8.562%	$69.8814	$69.88	$69.90	$69.90
Purchase #6	$233.41	5.607%	$246.4973	$246.50	$246.50	$246.50
Purchase #7	$59.83	4.589%	$62.5756	$62.58	$62.60	$62.60
7 purchase totals =	$811.29		$877.5495	$877.56	$877.55	$877.60