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	$31.37	3.844%	$32.5759	$32.58	$32.60	$32.60
Purchase #2	$82.49	11.492%	$91.9698	$91.97	$91.95	$92.00
Purchase #3	$114.80	11.423%	$127.9136	$127.91	$127.90	$127.90
Purchase #4	$72.92	8.153%	$78.8652	$78.87	$78.85	$78.90
Purchase #5	$47.73	7.213%	$51.1728	$51.17	$51.15	$51.20
Purchase #6	$233.73	6.827%	$249.6867	$249.69	$249.70	$249.70
Purchase #7	$54.47	5.147%	$57.2736	$57.27	$57.25	$57.30
7 purchase totals =	$637.51		$689.4576	$689.46	$689.40	$689.60