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	$60.38	3.401%	$62.4335	$62.43	$62.45	$62.40
Purchase #2	$66.99	7.703%	$72.1502	$72.15	$72.15	$72.20
Purchase #3	$30.36	10.535%	$33.5584	$33.56	$33.55	$33.60
Purchase #4	$85.28	13.637%	$96.9096	$96.91	$96.90	$96.90
Purchase #5	$48.48	9.523%	$53.0968	$53.10	$53.10	$53.10
Purchase #6	$108.81	9.309%	$118.9391	$118.94	$118.95	$118.90
Purchase #7	$92.44	13.847%	$105.2402	$105.24	$105.25	$105.20
7 purchase totals =	$492.74		$542.3278	$542.33	$542.35	$542.30