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	$64.40	4.133%	$67.0617	$67.06	$67.05	$67.10
Purchase #2	$151.50	10.381%	$167.2272	$167.23	$167.25	$167.20
Purchase #3	$110.40	6.154%	$117.194	$117.19	$117.20	$117.20
Purchase #4	$59.73	4.630%	$62.4955	$62.50	$62.50	$62.50
Purchase #5	$202.87	4.471%	$211.9403	$211.94	$211.95	$211.90
Purchase #6	$234.40	11.157%	$260.552	$260.55	$260.55	$260.60
Purchase #7	$118.73	12.351%	$133.3943	$133.39	$133.40	$133.40
7 purchase totals =	$942.03		$1,019.8650	$1,019.86	$1,019.90	$1,019.90