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	$42.50	8.591%	$46.1512	$46.15	$46.15	$46.20
Purchase #2	$32.66	3.550%	$33.8194	$33.82	$33.80	$33.80
Purchase #3	$214.36	13.587%	$243.4851	$243.49	$243.50	$243.50
Purchase #4	$250.69	12.713%	$282.5602	$282.56	$282.55	$282.60
Purchase #5	$54.71	8.195%	$59.1935	$59.19	$59.20	$59.20
Purchase #6	$40.38	10.207%	$44.5016	$44.50	$44.50	$44.50
Purchase #7	$99.50	5.286%	$104.7596	$104.76	$104.75	$104.80
7 purchase totals =	$734.80		$814.4706	$814.47	$814.45	$814.60