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	$209.32	6.647%	$223.2335	$223.23	$223.25	$223.20
Purchase #2	$195.57	7.386%	$210.0148	$210.01	$210.00	$210.00
Purchase #3	$132.31	6.333%	$140.6892	$140.69	$140.70	$140.70
Purchase #4	$166.37	5.678%	$175.8165	$175.82	$175.80	$175.80
Purchase #5	$250.94	11.737%	$280.3928	$280.39	$280.40	$280.40
Purchase #6	$16.69	11.625%	$18.6302	$18.63	$18.65	$18.60
Purchase #7	$131.63	4.498%	$137.5507	$137.55	$137.55	$137.60
7 purchase totals =	$1,102.83		$1,186.3277	$1,186.32	$1,186.35	$1,186.30