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	$181.91	12.260%	$204.2122	$204.21	$204.20	$204.20
Purchase #2	$198.55	6.480%	$211.416	$211.42	$211.40	$211.40
Purchase #3	$33.70	5.191%	$35.4494	$35.45	$35.45	$35.40
Purchase #4	$204.28	5.522%	$215.5603	$215.56	$215.55	$215.60
Purchase #5	$31.75	5.484%	$33.4912	$33.49	$33.50	$33.50
Purchase #6	$175.69	8.645%	$190.8784	$190.88	$190.90	$190.90
Purchase #7	$184.92	3.800%	$191.947	$191.95	$191.95	$191.90
7 purchase totals =	$1,010.80		$1,082.9545	$1,082.96	$1,082.95	$1,082.90