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	$61.88	9.517%	$67.7691	$67.77	$67.75	$67.80
Purchase #2	$192.92	10.522%	$213.219	$213.22	$213.20	$213.20
Purchase #3	$90.79	6.190%	$96.4099	$96.41	$96.40	$96.40
Purchase #4	$82.93	7.788%	$89.3886	$89.39	$89.40	$89.40
Purchase #5	$223.60	9.379%	$244.5714	$244.57	$244.55	$244.60
Purchase #6	$189.72	7.128%	$203.2432	$203.24	$203.25	$203.20
Purchase #7	$172.83	5.511%	$182.3547	$182.35	$182.35	$182.40
7 purchase totals =	$1,014.67		$1,096.9559	$1,096.95	$1,096.90	$1,097.00