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	$86.31	4.706%	$90.3717	$90.37	$90.35	$90.40
Purchase #2	$217.85	10.166%	$239.9966	$240.00	$240.00	$240.00
Purchase #3	$61.56	6.410%	$65.506	$65.51	$65.50	$65.50
Purchase #4	$71.90	12.273%	$80.7243	$80.72	$80.70	$80.70
Purchase #5	$201.44	13.352%	$228.3363	$228.34	$228.35	$228.30
Purchase #6	$168.97	13.140%	$191.1727	$191.17	$191.15	$191.20
Purchase #7	$154.25	7.820%	$166.3124	$166.31	$166.30	$166.30
7 purchase totals =	$962.28		$1,062.4200	$1,062.42	$1,062.35	$1,062.40