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	$67.81	7.544%	$72.9256	$72.93	$72.95	$72.90
Purchase #2	$242.49	7.829%	$261.4745	$261.47	$261.45	$261.50
Purchase #3	$148.98	9.104%	$162.5431	$162.54	$162.55	$162.50
Purchase #4	$172.74	12.538%	$194.3981	$194.40	$194.40	$194.40
Purchase #5	$48.54	11.419%	$54.0828	$54.08	$54.10	$54.10
Purchase #6	$161.56	8.378%	$175.0955	$175.10	$175.10	$175.10
Purchase #7	$214.93	3.161%	$221.7239	$221.72	$221.70	$221.70
7 purchase totals =	$1,057.05		$1,142.2435	$1,142.24	$1,142.25	$1,142.20