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	$141.99	6.136%	$150.7025	$150.70	$150.70	$150.70
Purchase #2	$87.74	10.565%	$97.0097	$97.01	$97.00	$97.00
Purchase #3	$249.86	9.328%	$273.1669	$273.17	$273.15	$273.20
Purchase #4	$152.59	7.668%	$164.2906	$164.29	$164.30	$164.30
Purchase #5	$80.58	11.144%	$89.5598	$89.56	$89.55	$89.60
Purchase #6	$195.53	10.807%	$216.6609	$216.66	$216.65	$216.70
Purchase #7	$90.49	13.687%	$102.8754	$102.88	$102.90	$102.90
7 purchase totals =	$998.78		$1,094.2658	$1,094.27	$1,094.25	$1,094.40