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	$169.42	9.372%	$185.298	$185.30	$185.30	$185.30
Purchase #2	$125.53	11.466%	$139.9233	$139.92	$139.90	$139.90
Purchase #3	$100.56	8.436%	$109.0432	$109.04	$109.05	$109.00
Purchase #4	$58.58	5.751%	$61.9489	$61.95	$61.95	$61.90
Purchase #5	$196.26	8.821%	$213.5721	$213.57	$213.55	$213.60
Purchase #6	$247.37	9.613%	$271.1497	$271.15	$271.15	$271.10
Purchase #7	$81.25	9.617%	$89.0638	$89.06	$89.05	$89.10
7 purchase totals =	$978.97		$1,069.9990	$1,069.99	$1,069.95	$1,069.90