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	$146.46	11.230%	$162.9075	$162.91	$162.90	$162.90
Purchase #2	$6.38	12.567%	$7.1818	$7.18	$7.20	$7.20
Purchase #3	$175.37	5.355%	$184.7611	$184.76	$184.75	$184.80
Purchase #4	$86.73	8.599%	$94.1879	$94.19	$94.20	$94.20
Purchase #5	$95.35	10.319%	$105.1892	$105.19	$105.20	$105.20
Purchase #6	$19.86	3.539%	$20.5628	$20.56	$20.55	$20.60
Purchase #7	$39.44	6.677%	$42.0734	$42.07	$42.05	$42.10
7 purchase totals =	$569.59		$616.8637	$616.86	$616.85	$617.00