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	$61.97	3.734%	$64.284	$64.28	$64.30	$64.30
Purchase #2	$86.92	4.594%	$90.9131	$90.91	$90.90	$90.90
Purchase #3	$68.81	4.810%	$72.1198	$72.12	$72.10	$72.10
Purchase #4	$45.64	13.858%	$51.9648	$51.96	$51.95	$52.00
Purchase #5	$115.66	7.191%	$123.9771	$123.98	$124.00	$124.00
Purchase #6	$196.45	3.221%	$202.7777	$202.78	$202.80	$202.80
Purchase #7	$53.58	6.535%	$57.0815	$57.08	$57.10	$57.10
7 purchase totals =	$629.03		$663.1180	$663.11	$663.15	$663.20