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	$201.96	12.407%	$227.0172	$227.02	$227.00	$227.00
Purchase #2	$53.47	3.744%	$55.4719	$55.47	$55.45	$55.50
Purchase #3	$162.41	6.295%	$172.6337	$172.63	$172.65	$172.60
Purchase #4	$233.55	13.179%	$264.3296	$264.33	$264.35	$264.30
Purchase #5	$214.31	13.526%	$243.2976	$243.30	$243.30	$243.30
Purchase #6	$92.98	4.307%	$96.9846	$96.98	$97.00	$97.00
Purchase #7	$50.82	5.482%	$53.606	$53.61	$53.60	$53.60
7 purchase totals =	$1,009.50		$1,113.3406	$1,113.34	$1,113.35	$1,113.30