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	$59.69	12.349%	$67.0611	$67.06	$67.05	$67.10
Purchase #2	$36.68	3.471%	$37.9532	$37.95	$37.95	$38.00
Purchase #3	$245.68	10.193%	$270.7222	$270.72	$270.70	$270.70
Purchase #4	$134.26	6.223%	$142.615	$142.62	$142.60	$142.60
Purchase #5	$79.66	4.124%	$82.9452	$82.95	$82.95	$82.90
Purchase #6	$68.38	5.140%	$71.8947	$71.89	$71.90	$71.90
Purchase #7	$103.98	12.649%	$117.1324	$117.13	$117.15	$117.10
7 purchase totals =	$728.33		$790.3238	$790.32	$790.30	$790.30