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	$157.91	10.716%	$174.8316	$174.83	$174.85	$174.80
Purchase #2	$90.82	13.697%	$103.2596	$103.26	$103.25	$103.30
Purchase #3	$168.62	10.635%	$186.5527	$186.55	$186.55	$186.60
Purchase #4	$218.94	6.601%	$233.3922	$233.39	$233.40	$233.40
Purchase #5	$234.41	12.606%	$263.9597	$263.96	$263.95	$264.00
Purchase #6	$67.42	5.851%	$71.3647	$71.36	$71.35	$71.40
Purchase #7	$15.77	11.463%	$17.5777	$17.58	$17.60	$17.60
7 purchase totals =	$953.89		$1,050.9382	$1,050.93	$1,050.95	$1,051.10