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	$145.71	11.629%	$162.6546	$162.65	$162.65	$162.70
Purchase #2	$82.48	9.779%	$90.5457	$90.55	$90.55	$90.50
Purchase #3	$127.65	12.161%	$143.1735	$143.17	$143.15	$143.20
Purchase #4	$77.77	9.464%	$85.1302	$85.13	$85.15	$85.10
Purchase #5	$232.92	10.270%	$256.8409	$256.84	$256.85	$256.80
Purchase #6	$238.36	3.704%	$247.1889	$247.19	$247.20	$247.20
Purchase #7	$241.38	3.472%	$249.7607	$249.76	$249.75	$249.80
7 purchase totals =	$1,146.27		$1,235.2945	$1,235.29	$1,235.30	$1,235.30