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	$177.56	8.215%	$192.1466	$192.15	$192.15	$192.10
Purchase #2	$38.48	11.671%	$42.971	$42.97	$42.95	$43.00
Purchase #3	$175.53	5.274%	$184.7875	$184.79	$184.80	$184.80
Purchase #4	$68.27	4.711%	$71.4862	$71.49	$71.50	$71.50
Purchase #5	$166.32	3.219%	$171.6738	$171.67	$171.65	$171.70
Purchase #6	$155.71	7.132%	$166.8152	$166.82	$166.80	$166.80
Purchase #7	$37.98	8.841%	$41.3378	$41.34	$41.35	$41.30
7 purchase totals =	$819.85		$871.2181	$871.23	$871.20	$871.20