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	$189.37	6.116%	$200.9519	$200.95	$200.95	$201.00
Purchase #2	$128.43	7.321%	$137.8324	$137.83	$137.85	$137.80
Purchase #3	$74.79	10.611%	$82.726	$82.73	$82.75	$82.70
Purchase #4	$86.53	7.834%	$93.3088	$93.31	$93.30	$93.30
Purchase #5	$88.32	12.379%	$99.2531	$99.25	$99.25	$99.30
Purchase #6	$199.62	5.712%	$211.0223	$211.02	$211.00	$211.00
Purchase #7	$245.67	11.380%	$273.6272	$273.63	$273.65	$273.60
7 purchase totals =	$1,012.73		$1,098.7217	$1,098.72	$1,098.75	$1,098.70