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	$91.83	13.586%	$104.306	$104.31	$104.30	$104.30
Purchase #2	$155.80	12.452%	$175.2002	$175.20	$175.20	$175.20
Purchase #3	$194.96	10.735%	$215.889	$215.89	$215.90	$215.90
Purchase #4	$15.51	7.117%	$16.6138	$16.61	$16.60	$16.60
Purchase #5	$42.65	6.399%	$45.3792	$45.38	$45.40	$45.40
Purchase #6	$101.43	7.841%	$109.3831	$109.38	$109.40	$109.40
Purchase #7	$45.91	13.490%	$52.1033	$52.10	$52.10	$52.10
7 purchase totals =	$648.09		$718.8746	$718.87	$718.90	$718.90