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	$206.46	5.807%	$218.4491	$218.45	$218.45	$218.40
Purchase #2	$181.76	6.285%	$193.1836	$193.18	$193.20	$193.20
Purchase #3	$152.40	10.850%	$168.9354	$168.94	$168.95	$168.90
Purchase #4	$75.98	7.259%	$81.4954	$81.50	$81.50	$81.50
Purchase #5	$34.57	7.454%	$37.1468	$37.15	$37.15	$37.10
Purchase #6	$150.63	3.874%	$156.4654	$156.47	$156.45	$156.50
Purchase #7	$135.45	12.111%	$151.8543	$151.85	$151.85	$151.90
7 purchase totals =	$937.25		$1,007.5300	$1,007.54	$1,007.55	$1,007.50