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	$241.27	3.250%	$249.1113	$249.11	$249.10	$249.10
Purchase #2	$48.72	7.400%	$52.3253	$52.33	$52.35	$52.30
Purchase #3	$227.67	8.501%	$247.0242	$247.02	$247.00	$247.00
Purchase #4	$65.47	13.713%	$74.4479	$74.45	$74.45	$74.40
Purchase #5	$81.35	5.593%	$85.8999	$85.90	$85.90	$85.90
Purchase #6	$142.46	8.459%	$154.5107	$154.51	$154.50	$154.50
Purchase #7	$162.35	3.752%	$168.4414	$168.44	$168.45	$168.40
7 purchase totals =	$969.29		$1,031.7607	$1,031.76	$1,031.75	$1,031.60