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	$67.36	6.726%	$71.8906	$71.89	$71.90	$71.90
Purchase #2	$101.50	9.410%	$111.0512	$111.05	$111.05	$111.10
Purchase #3	$17.31	4.430%	$18.0768	$18.08	$18.10	$18.10
Purchase #4	$15.32	10.132%	$16.8722	$16.87	$16.85	$16.90
Purchase #5	$90.63	11.510%	$101.0615	$101.06	$101.05	$101.10
Purchase #6	$100.46	11.830%	$112.3444	$112.34	$112.35	$112.30
Purchase #7	$42.97	3.593%	$44.5139	$44.51	$44.50	$44.50
7 purchase totals =	$435.55		$475.8106	$475.80	$475.80	$475.90