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	$168.72	11.857%	$188.7251	$188.73	$188.75	$188.70
Purchase #2	$218.42	7.361%	$234.4979	$234.50	$234.50	$234.50
Purchase #3	$187.71	5.791%	$198.5803	$198.58	$198.60	$198.60
Purchase #4	$92.96	13.737%	$105.7299	$105.73	$105.75	$105.70
Purchase #5	$142.85	9.270%	$156.0922	$156.09	$156.10	$156.10
Purchase #6	$40.46	7.187%	$43.3679	$43.37	$43.35	$43.40
Purchase #7	$39.89	13.317%	$45.2022	$45.20	$45.20	$45.20
7 purchase totals =	$891.01		$972.1955	$972.20	$972.25	$972.20