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	$190.59	3.135%	$196.565	$196.57	$196.55	$196.60
Purchase #2	$196.73	7.696%	$211.8703	$211.87	$211.85	$211.90
Purchase #3	$155.62	10.661%	$172.2106	$172.21	$172.20	$172.20
Purchase #4	$28.96	10.215%	$31.9183	$31.92	$31.90	$31.90
Purchase #5	$246.45	9.735%	$270.4419	$270.44	$270.45	$270.40
Purchase #6	$40.28	4.395%	$42.0503	$42.05	$42.05	$42.10
Purchase #7	$82.74	10.472%	$91.4045	$91.40	$91.40	$91.40
7 purchase totals =	$941.37		$1,016.4609	$1,016.46	$1,016.40	$1,016.50