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	$131.93	12.311%	$148.1719	$148.17	$148.15	$148.20
Purchase #2	$48.87	9.184%	$53.3582	$53.36	$53.35	$53.40
Purchase #3	$127.41	13.711%	$144.8792	$144.88	$144.90	$144.90
Purchase #4	$200.90	7.196%	$215.3568	$215.36	$215.35	$215.40
Purchase #5	$96.84	6.623%	$103.2537	$103.25	$103.25	$103.30
Purchase #6	$5.64	9.238%	$6.161	$6.16	$6.15	$6.20
Purchase #7	$249.85	7.613%	$268.8711	$268.87	$268.85	$268.90
7 purchase totals =	$861.44		$940.0519	$940.05	$940.00	$940.30