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	$35.88	6.738%	$38.2976	$38.30	$38.30	$38.30
Purchase #2	$176.83	11.346%	$196.8931	$196.89	$196.90	$196.90
Purchase #3	$47.84	11.340%	$53.2651	$53.27	$53.25	$53.30
Purchase #4	$207.78	7.401%	$223.1578	$223.16	$223.15	$223.20
Purchase #5	$144.26	4.835%	$151.235	$151.24	$151.25	$151.20
Purchase #6	$141.77	8.299%	$153.5355	$153.54	$153.55	$153.50
Purchase #7	$188.60	6.565%	$200.9816	$200.98	$201.00	$201.00
7 purchase totals =	$942.96		$1,017.3657	$1,017.38	$1,017.40	$1,017.40