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	$206.93	10.597%	$228.8584	$228.86	$228.85	$228.90
Purchase #2	$152.78	3.315%	$157.8447	$157.84	$157.85	$157.80
Purchase #3	$90.30	10.801%	$100.0533	$100.05	$100.05	$100.10
Purchase #4	$201.56	9.584%	$220.8775	$220.88	$220.90	$220.90
Purchase #5	$77.52	3.726%	$80.4084	$80.41	$80.40	$80.40
Purchase #6	$129.48	7.674%	$139.4163	$139.42	$139.40	$139.40
Purchase #7	$207.72	10.234%	$228.9781	$228.98	$229.00	$229.00
7 purchase totals =	$1,066.29		$1,156.4367	$1,156.44	$1,156.45	$1,156.50