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	$118.80	8.796%	$129.2496	$129.25	$129.25	$129.20
Purchase #2	$55.53	6.819%	$59.3166	$59.32	$59.30	$59.30
Purchase #3	$166.56	5.528%	$175.7674	$175.77	$175.75	$175.80
Purchase #4	$29.93	4.292%	$31.2146	$31.21	$31.20	$31.20
Purchase #5	$84.51	13.158%	$95.6298	$95.63	$95.65	$95.60
Purchase #6	$131.98	8.286%	$142.9159	$142.92	$142.90	$142.90
Purchase #7	$133.25	4.564%	$139.3315	$139.33	$139.35	$139.30
7 purchase totals =	$720.56		$773.4254	$773.43	$773.40	$773.30