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	$207.39	10.200%	$228.5438	$228.54	$228.55	$228.50
Purchase #2	$176.63	13.416%	$200.3267	$200.33	$200.35	$200.30
Purchase #3	$97.60	6.234%	$103.6844	$103.68	$103.70	$103.70
Purchase #4	$24.36	4.862%	$25.5444	$25.54	$25.55	$25.50
Purchase #5	$147.56	11.466%	$164.4792	$164.48	$164.50	$164.50
Purchase #6	$167.25	3.663%	$173.3764	$173.38	$173.40	$173.40
Purchase #7	$125.72	3.806%	$130.5049	$130.50	$130.50	$130.50
7 purchase totals =	$946.51		$1,026.4598	$1,026.45	$1,026.55	$1,026.40