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	$56.52	10.303%	$62.3433	$62.34	$62.35	$62.30
Purchase #2	$56.70	10.322%	$62.5526	$62.55	$62.55	$62.60
Purchase #3	$88.73	12.264%	$99.6118	$99.61	$99.60	$99.60
Purchase #4	$9.37	7.392%	$10.0626	$10.06	$10.05	$10.10
Purchase #5	$121.87	6.351%	$129.61	$129.61	$129.60	$129.60
Purchase #6	$241.25	12.216%	$270.7211	$270.72	$270.70	$270.70
Purchase #7	$68.89	3.795%	$71.5044	$71.50	$71.50	$71.50
7 purchase totals =	$643.33		$706.4058	$706.39	$706.35	$706.40