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	$68.32	5.409%	$72.0154	$72.02	$72.00	$72.00
Purchase #2	$74.28	5.253%	$78.1819	$78.18	$78.20	$78.20
Purchase #3	$154.91	10.260%	$170.8038	$170.80	$170.80	$170.80
Purchase #4	$108.65	3.144%	$112.066	$112.07	$112.05	$112.10
Purchase #5	$215.51	13.156%	$243.8625	$243.86	$243.85	$243.90
Purchase #6	$102.73	7.414%	$110.3464	$110.35	$110.35	$110.30
Purchase #7	$71.77	9.614%	$78.67	$78.67	$78.65	$78.70
7 purchase totals =	$796.17		$865.9460	$865.95	$865.90	$866.00