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	$228.47	7.477%	$245.5527	$245.55	$245.55	$245.60
Purchase #2	$61.63	10.164%	$67.8941	$67.89	$67.90	$67.90
Purchase #3	$176.36	5.806%	$186.5995	$186.60	$186.60	$186.60
Purchase #4	$236.63	13.510%	$268.5987	$268.60	$268.60	$268.60
Purchase #5	$100.84	7.474%	$108.3768	$108.38	$108.40	$108.40
Purchase #6	$65.68	8.231%	$71.0861	$71.09	$71.10	$71.10
Purchase #7	$97.45	12.193%	$109.3321	$109.33	$109.35	$109.30
7 purchase totals =	$967.06		$1,057.4400	$1,057.44	$1,057.50	$1,057.50