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	$110.26	5.650%	$116.4897	$116.49	$116.50	$116.50
Purchase #2	$164.56	13.207%	$186.2934	$186.29	$186.30	$186.30
Purchase #3	$45.94	3.200%	$47.4101	$47.41	$47.40	$47.40
Purchase #4	$38.47	7.379%	$41.3087	$41.31	$41.30	$41.30
Purchase #5	$33.36	13.258%	$37.7829	$37.78	$37.80	$37.80
Purchase #6	$5.98	12.421%	$6.7228	$6.72	$6.70	$6.70
Purchase #7	$86.61	5.464%	$91.3424	$91.34	$91.35	$91.30
7 purchase totals =	$485.18		$527.3500	$527.34	$527.35	$527.30