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	$141.46	13.714%	$160.8598	$160.86	$160.85	$160.90
Purchase #2	$81.98	8.756%	$89.1582	$89.16	$89.15	$89.20
Purchase #3	$233.68	6.431%	$248.708	$248.71	$248.70	$248.70
Purchase #4	$162.73	11.454%	$181.3691	$181.37	$181.35	$181.40
Purchase #5	$161.41	11.204%	$179.4944	$179.49	$179.50	$179.50
Purchase #6	$127.89	9.704%	$140.3004	$140.30	$140.30	$140.30
Purchase #7	$70.98	8.821%	$77.2411	$77.24	$77.25	$77.20
7 purchase totals =	$980.13		$1,077.1310	$1,077.13	$1,077.10	$1,077.20