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	$191.33	9.761%	$210.0057	$210.01	$210.00	$210.00
Purchase #2	$219.50	9.556%	$240.4754	$240.48	$240.50	$240.50
Purchase #3	$33.54	10.828%	$37.1717	$37.17	$37.15	$37.20
Purchase #4	$152.38	3.402%	$157.564	$157.56	$157.55	$157.60
Purchase #5	$72.93	13.640%	$82.8777	$82.88	$82.90	$82.90
Purchase #6	$141.49	10.772%	$156.7313	$156.73	$156.75	$156.70
Purchase #7	$54.34	13.237%	$61.533	$61.53	$61.55	$61.50
7 purchase totals =	$865.51		$946.3588	$946.36	$946.40	$946.40