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	$176.41	4.479%	$184.3114	$184.31	$184.30	$184.30
Purchase #2	$128.61	8.522%	$139.5701	$139.57	$139.55	$139.60
Purchase #3	$82.65	8.696%	$89.8372	$89.84	$89.85	$89.80
Purchase #4	$239.48	6.599%	$255.2833	$255.28	$255.30	$255.30
Purchase #5	$41.50	4.315%	$43.2907	$43.29	$43.30	$43.30
Purchase #6	$192.95	4.610%	$201.845	$201.85	$201.85	$201.80
Purchase #7	$63.66	6.192%	$67.6018	$67.60	$67.60	$67.60
7 purchase totals =	$925.26		$981.7395	$981.74	$981.75	$981.70