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	$93.42	11.521%	$104.1829	$104.18	$104.20	$104.20
Purchase #2	$144.45	12.807%	$162.9497	$162.95	$162.95	$162.90
Purchase #3	$186.69	7.623%	$200.9214	$200.92	$200.90	$200.90
Purchase #4	$98.89	6.814%	$105.6284	$105.63	$105.65	$105.60
Purchase #5	$100.67	4.729%	$105.4307	$105.43	$105.45	$105.40
Purchase #6	$81.77	11.783%	$91.405	$91.41	$91.40	$91.40
Purchase #7	$249.34	9.672%	$273.4562	$273.46	$273.45	$273.50
7 purchase totals =	$955.23		$1,043.9743	$1,043.98	$1,044.00	$1,043.90