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	$72.36	13.653%	$82.2393	$82.24	$82.25	$82.20
Purchase #2	$203.43	6.332%	$216.3112	$216.31	$216.30	$216.30
Purchase #3	$134.88	9.658%	$147.9067	$147.91	$147.90	$147.90
Purchase #4	$58.57	6.532%	$62.3958	$62.40	$62.40	$62.40
Purchase #5	$236.44	10.334%	$260.8737	$260.87	$260.85	$260.90
Purchase #6	$87.58	13.660%	$99.5434	$99.54	$99.55	$99.50
Purchase #7	$131.87	13.609%	$149.8162	$149.82	$149.80	$149.80
7 purchase totals =	$925.13		$1,019.0863	$1,019.09	$1,019.05	$1,019.00