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	$105.41	9.492%	$115.4155	$115.42	$115.40	$115.40
Purchase #2	$199.51	6.561%	$212.5999	$212.60	$212.60	$212.60
Purchase #3	$54.87	8.229%	$59.3853	$59.39	$59.40	$59.40
Purchase #4	$41.92	9.228%	$45.7884	$45.79	$45.80	$45.80
Purchase #5	$31.87	7.294%	$34.1946	$34.19	$34.20	$34.20
Purchase #6	$144.53	12.269%	$162.2624	$162.26	$162.25	$162.30
Purchase #7	$90.99	9.457%	$99.5949	$99.59	$99.60	$99.60
7 purchase totals =	$669.10		$729.2410	$729.24	$729.25	$729.30