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	$152.40	10.641%	$168.6169	$168.62	$168.60	$168.60
Purchase #2	$214.30	13.185%	$242.5555	$242.56	$242.55	$242.60
Purchase #3	$181.52	3.631%	$188.111	$188.11	$188.10	$188.10
Purchase #4	$41.89	12.228%	$47.0123	$47.01	$47.00	$47.00
Purchase #5	$26.69	3.184%	$27.5398	$27.54	$27.55	$27.50
Purchase #6	$153.41	13.773%	$174.5392	$174.54	$174.55	$174.50
Purchase #7	$74.82	9.298%	$81.7768	$81.78	$81.80	$81.80
7 purchase totals =	$845.03		$930.1515	$930.16	$930.15	$930.10