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	$110.59	5.483%	$116.6536	$116.65	$116.65	$116.70
Purchase #2	$146.77	6.173%	$155.8301	$155.83	$155.85	$155.80
Purchase #3	$80.55	7.174%	$86.3287	$86.33	$86.35	$86.30
Purchase #4	$83.41	6.805%	$89.0861	$89.09	$89.10	$89.10
Purchase #5	$94.94	10.661%	$105.0616	$105.06	$105.05	$105.10
Purchase #6	$156.64	5.513%	$165.2756	$165.28	$165.30	$165.30
Purchase #7	$249.45	3.190%	$257.4075	$257.41	$257.40	$257.40
7 purchase totals =	$922.35		$975.6432	$975.65	$975.70	$975.70