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	$240.92	9.548%	$263.923	$263.92	$263.90	$263.90
Purchase #2	$155.96	4.233%	$162.5618	$162.56	$162.55	$162.60
Purchase #3	$213.62	7.535%	$229.7163	$229.72	$229.70	$229.70
Purchase #4	$181.32	10.553%	$200.4547	$200.45	$200.45	$200.50
Purchase #5	$81.66	11.518%	$91.0656	$91.07	$91.05	$91.10
Purchase #6	$156.67	4.769%	$164.1416	$164.14	$164.15	$164.10
Purchase #7	$41.88	9.268%	$45.7614	$45.76	$45.75	$45.80
7 purchase totals =	$1,072.03		$1,157.6244	$1,157.62	$1,157.55	$1,157.70