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	$249.62	11.700%	$278.8255	$278.83	$278.85	$278.80
Purchase #2	$5.64	10.527%	$6.2337	$6.23	$6.25	$6.20
Purchase #3	$37.78	5.132%	$39.7189	$39.72	$39.70	$39.70
Purchase #4	$110.34	3.192%	$113.8621	$113.86	$113.85	$113.90
Purchase #5	$134.34	8.608%	$145.904	$145.90	$145.90	$145.90
Purchase #6	$167.62	12.325%	$188.2792	$188.28	$188.30	$188.30
Purchase #7	$213.94	7.219%	$229.3843	$229.38	$229.40	$229.40
7 purchase totals =	$919.28		$1,002.2077	$1,002.20	$1,002.25	$1,002.20