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	$147.52	3.233%	$152.2893	$152.29	$152.30	$152.30
Purchase #2	$168.41	13.723%	$191.5209	$191.52	$191.50	$191.50
Purchase #3	$37.62	12.650%	$42.3789	$42.38	$42.40	$42.40
Purchase #4	$240.83	13.664%	$273.737	$273.74	$273.75	$273.70
Purchase #5	$177.93	4.538%	$186.0045	$186.00	$186.00	$186.00
Purchase #6	$101.91	5.831%	$107.8524	$107.85	$107.85	$107.90
Purchase #7	$177.62	7.288%	$190.5649	$190.56	$190.55	$190.60
7 purchase totals =	$1,051.84		$1,144.3479	$1,144.34	$1,144.35	$1,144.40