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	$158.43	4.130%	$164.9732	$164.97	$164.95	$165.00
Purchase #2	$42.37	8.249%	$45.8651	$45.87	$45.85	$45.90
Purchase #3	$37.63	6.107%	$39.9281	$39.93	$39.95	$39.90
Purchase #4	$43.27	5.763%	$45.7637	$45.76	$45.75	$45.80
Purchase #5	$99.36	4.279%	$103.6116	$103.61	$103.60	$103.60
Purchase #6	$210.33	4.196%	$219.1554	$219.16	$219.15	$219.20
Purchase #7	$82.66	5.179%	$86.941	$86.94	$86.95	$86.90
7 purchase totals =	$674.05		$706.2381	$706.24	$706.20	$706.30