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	$142.60	5.874%	$150.9763	$150.98	$151.00	$151.00
Purchase #2	$171.65	5.710%	$181.4512	$181.45	$181.45	$181.50
Purchase #3	$156.51	3.670%	$162.2539	$162.25	$162.25	$162.30
Purchase #4	$182.42	12.866%	$205.8902	$205.89	$205.90	$205.90
Purchase #5	$180.25	6.549%	$192.0546	$192.05	$192.05	$192.10
Purchase #6	$184.25	6.680%	$196.5579	$196.56	$196.55	$196.60
Purchase #7	$212.70	5.130%	$223.6115	$223.61	$223.60	$223.60
7 purchase totals =	$1,230.38		$1,312.7956	$1,312.79	$1,312.80	$1,313.00