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	$172.96	6.417%	$184.0588	$184.06	$184.05	$184.10
Purchase #2	$6.63	13.732%	$7.5404	$7.54	$7.55	$7.50
Purchase #3	$223.43	7.299%	$239.7382	$239.74	$239.75	$239.70
Purchase #4	$20.88	4.382%	$21.795	$21.80	$21.80	$21.80
Purchase #5	$203.97	7.555%	$219.3799	$219.38	$219.40	$219.40
Purchase #6	$73.72	11.758%	$82.388	$82.39	$82.40	$82.40
Purchase #7	$43.41	4.700%	$45.4503	$45.45	$45.45	$45.50
7 purchase totals =	$745.00		$800.3506	$800.36	$800.40	$800.40