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	$187.83	4.234%	$195.7827	$195.78	$195.80	$195.80
Purchase #2	$94.82	4.102%	$98.7095	$98.71	$98.70	$98.70
Purchase #3	$177.58	6.375%	$188.9007	$188.90	$188.90	$188.90
Purchase #4	$116.32	10.337%	$128.344	$128.34	$128.35	$128.30
Purchase #5	$153.76	6.703%	$164.0665	$164.07	$164.05	$164.10
Purchase #6	$245.85	10.426%	$271.4823	$271.48	$271.50	$271.50
Purchase #7	$193.60	3.751%	$200.8619	$200.86	$200.85	$200.90
7 purchase totals =	$1,169.76		$1,248.1476	$1,248.14	$1,248.15	$1,248.20