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	$157.56	13.330%	$178.5627	$178.56	$178.55	$178.60
Purchase #2	$26.67	8.336%	$28.8932	$28.89	$28.90	$28.90
Purchase #3	$54.79	12.442%	$61.607	$61.61	$61.60	$61.60
Purchase #4	$89.85	9.787%	$98.6436	$98.64	$98.65	$98.60
Purchase #5	$93.86	6.795%	$100.2378	$100.24	$100.25	$100.20
Purchase #6	$249.41	7.692%	$268.5946	$268.59	$268.60	$268.60
Purchase #7	$160.86	9.343%	$175.8891	$175.89	$175.90	$175.90
7 purchase totals =	$833.00		$912.4280	$912.42	$912.45	$912.40