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	$164.42	11.437%	$183.2247	$183.22	$183.20	$183.20
Purchase #2	$189.47	5.772%	$200.4062	$200.41	$200.40	$200.40
Purchase #3	$100.40	3.130%	$103.5425	$103.54	$103.55	$103.50
Purchase #4	$55.63	7.443%	$59.7705	$59.77	$59.75	$59.80
Purchase #5	$242.49	4.757%	$254.0252	$254.03	$254.05	$254.00
Purchase #6	$70.56	9.839%	$77.5024	$77.50	$77.50	$77.50
Purchase #7	$60.86	7.208%	$65.2468	$65.25	$65.25	$65.20
7 purchase totals =	$883.83		$943.7183	$943.72	$943.70	$943.60