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	$131.58	11.560%	$146.7906	$146.79	$146.80	$146.80
Purchase #2	$29.83	7.115%	$31.9524	$31.95	$31.95	$32.00
Purchase #3	$134.36	13.274%	$152.1949	$152.19	$152.20	$152.20
Purchase #4	$100.29	8.689%	$109.0042	$109.00	$109.00	$109.00
Purchase #5	$56.52	8.459%	$61.301	$61.30	$61.30	$61.30
Purchase #6	$40.97	10.548%	$45.2915	$45.29	$45.30	$45.30
Purchase #7	$167.38	12.471%	$188.254	$188.25	$188.25	$188.30
7 purchase totals =	$660.93		$734.7886	$734.77	$734.80	$734.90