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	$168.31	4.164%	$175.3184	$175.32	$175.30	$175.30
Purchase #2	$130.72	7.864%	$140.9998	$141.00	$141.00	$141.00
Purchase #3	$58.78	3.506%	$60.8408	$60.84	$60.85	$60.80
Purchase #4	$104.53	9.577%	$114.5408	$114.54	$114.55	$114.50
Purchase #5	$240.65	12.163%	$269.9203	$269.92	$269.90	$269.90
Purchase #6	$91.95	10.746%	$101.8309	$101.83	$101.85	$101.80
Purchase #7	$141.27	9.270%	$154.3657	$154.37	$154.35	$154.40
7 purchase totals =	$936.21		$1,017.8167	$1,017.82	$1,017.80	$1,017.70