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	$30.59	12.686%	$34.4706	$34.47	$34.45	$34.50
Purchase #2	$190.61	12.305%	$214.0646	$214.06	$214.05	$214.10
Purchase #3	$141.73	6.712%	$151.2429	$151.24	$151.25	$151.20
Purchase #4	$245.38	7.549%	$263.9037	$263.90	$263.90	$263.90
Purchase #5	$87.33	13.702%	$99.296	$99.30	$99.30	$99.30
Purchase #6	$114.31	6.525%	$121.7687	$121.77	$121.75	$121.80
Purchase #7	$153.81	8.720%	$167.2222	$167.22	$167.20	$167.20
7 purchase totals =	$963.76		$1,051.9687	$1,051.96	$1,051.90	$1,052.00