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	$175.30	5.515%	$184.9678	$184.97	$184.95	$185.00
Purchase #2	$89.83	7.529%	$96.5933	$96.59	$96.60	$96.60
Purchase #3	$66.86	6.238%	$71.0307	$71.03	$71.05	$71.00
Purchase #4	$161.86	7.162%	$173.4524	$173.45	$173.45	$173.50
Purchase #5	$86.77	6.760%	$92.6357	$92.64	$92.65	$92.60
Purchase #6	$41.91	10.401%	$46.2691	$46.27	$46.25	$46.30
Purchase #7	$44.72	3.694%	$46.372	$46.37	$46.35	$46.40
7 purchase totals =	$667.25		$711.3210	$711.32	$711.30	$711.40