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	$15.54	3.754%	$16.1234	$16.12	$16.10	$16.10
Purchase #2	$117.54	7.366%	$126.198	$126.20	$126.20	$126.20
Purchase #3	$215.90	8.300%	$233.8197	$233.82	$233.80	$233.80
Purchase #4	$18.34	10.366%	$20.2411	$20.24	$20.25	$20.20
Purchase #5	$72.74	7.422%	$78.1388	$78.14	$78.15	$78.10
Purchase #6	$52.33	4.455%	$54.6613	$54.66	$54.65	$54.70
Purchase #7	$153.36	9.816%	$168.4138	$168.41	$168.40	$168.40
7 purchase totals =	$645.75		$697.5961	$697.59	$697.55	$697.50