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	$24.97	10.665%	$27.6331	$27.63	$27.65	$27.60
Purchase #2	$6.72	5.338%	$7.0787	$7.08	$7.10	$7.10
Purchase #3	$235.59	3.523%	$243.8898	$243.89	$243.90	$243.90
Purchase #4	$76.45	4.114%	$79.5952	$79.60	$79.60	$79.60
Purchase #5	$49.71	5.463%	$52.4257	$52.43	$52.45	$52.40
Purchase #6	$25.64	10.376%	$28.3004	$28.30	$28.30	$28.30
Purchase #7	$145.90	10.231%	$160.827	$160.83	$160.85	$160.80
7 purchase totals =	$564.98		$599.7499	$599.76	$599.85	$599.70