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	$203.30	4.867%	$213.1946	$213.19	$213.20	$213.20
Purchase #2	$119.76	3.112%	$123.4869	$123.49	$123.50	$123.50
Purchase #3	$241.92	3.559%	$250.5299	$250.53	$250.55	$250.50
Purchase #4	$190.52	4.168%	$198.4609	$198.46	$198.45	$198.50
Purchase #5	$141.42	9.305%	$154.5791	$154.58	$154.60	$154.60
Purchase #6	$54.97	9.741%	$60.3246	$60.32	$60.30	$60.30
Purchase #7	$133.85	9.423%	$146.4627	$146.46	$146.45	$146.50
7 purchase totals =	$1,085.74		$1,147.0387	$1,147.03	$1,147.05	$1,147.10