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	$52.50	6.495%	$55.9099	$55.91	$55.90	$55.90
Purchase #2	$162.83	5.183%	$171.2695	$171.27	$171.25	$171.30
Purchase #3	$80.96	5.595%	$85.4897	$85.49	$85.50	$85.50
Purchase #4	$241.60	5.461%	$254.7938	$254.79	$254.80	$254.80
Purchase #5	$178.67	4.135%	$186.058	$186.06	$186.05	$186.10
Purchase #6	$24.35	12.696%	$27.4415	$27.44	$27.45	$27.40
Purchase #7	$93.96	10.171%	$103.5167	$103.52	$103.50	$103.50
7 purchase totals =	$834.87		$884.4791	$884.48	$884.45	$884.50