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	$147.43	10.261%	$162.5578	$162.56	$162.55	$162.60
Purchase #2	$62.88	3.420%	$65.0305	$65.03	$65.05	$65.00
Purchase #3	$151.78	9.288%	$165.8773	$165.88	$165.90	$165.90
Purchase #4	$182.79	9.775%	$200.6577	$200.66	$200.65	$200.70
Purchase #5	$240.56	8.354%	$260.6564	$260.66	$260.65	$260.70
Purchase #6	$159.29	3.823%	$165.3797	$165.38	$165.40	$165.40
Purchase #7	$99.48	13.225%	$112.6362	$112.64	$112.65	$112.60
7 purchase totals =	$1,044.21		$1,132.7956	$1,132.81	$1,132.85	$1,132.90