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	$178.54	7.479%	$191.893	$191.89	$191.90	$191.90
Purchase #2	$40.45	12.255%	$45.4071	$45.41	$45.40	$45.40
Purchase #3	$210.45	5.606%	$222.2478	$222.25	$222.25	$222.20
Purchase #4	$248.50	6.107%	$263.6759	$263.68	$263.70	$263.70
Purchase #5	$90.28	9.253%	$98.6336	$98.63	$98.65	$98.60
Purchase #6	$103.96	9.672%	$114.015	$114.02	$114.00	$114.00
Purchase #7	$78.70	6.744%	$84.0075	$84.01	$84.00	$84.00
7 purchase totals =	$950.88		$1,019.8799	$1,019.89	$1,019.90	$1,019.80