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	$145.76	12.518%	$164.0062	$164.01	$164.00	$164.00
Purchase #2	$204.48	11.635%	$228.2712	$228.27	$228.25	$228.30
Purchase #3	$54.90	12.218%	$61.6077	$61.61	$61.60	$61.60
Purchase #4	$139.50	8.618%	$151.5221	$151.52	$151.50	$151.50
Purchase #5	$192.98	11.670%	$215.5008	$215.50	$215.50	$215.50
Purchase #6	$51.46	12.118%	$57.6959	$57.70	$57.70	$57.70
Purchase #7	$150.73	12.213%	$169.1387	$169.14	$169.15	$169.10
7 purchase totals =	$939.81		$1,047.7426	$1,047.75	$1,047.70	$1,047.70