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	$187.96	6.713%	$200.5778	$200.58	$200.60	$200.60
Purchase #2	$88.29	9.748%	$96.8965	$96.90	$96.90	$96.90
Purchase #3	$213.96	13.791%	$243.4672	$243.47	$243.45	$243.50
Purchase #4	$110.38	4.512%	$115.3603	$115.36	$115.35	$115.40
Purchase #5	$27.90	11.192%	$31.0226	$31.02	$31.00	$31.00
Purchase #6	$168.32	6.872%	$179.887	$179.89	$179.90	$179.90
Purchase #7	$161.62	11.586%	$180.3453	$180.35	$180.35	$180.30
7 purchase totals =	$958.43		$1,047.5567	$1,047.57	$1,047.55	$1,047.60