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	$150.66	9.689%	$165.2574	$165.26	$165.25	$165.30
Purchase #2	$163.86	4.707%	$171.5729	$171.57	$171.55	$171.60
Purchase #3	$104.85	4.791%	$109.8734	$109.87	$109.85	$109.90
Purchase #4	$61.25	8.416%	$66.4048	$66.40	$66.40	$66.40
Purchase #5	$53.88	10.310%	$59.435	$59.44	$59.45	$59.40
Purchase #6	$40.83	4.282%	$42.5783	$42.58	$42.60	$42.60
Purchase #7	$120.82	11.547%	$134.7711	$134.77	$134.75	$134.80
7 purchase totals =	$696.15		$749.8929	$749.89	$749.85	$750.00