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	$18.28	5.220%	$19.2342	$19.23	$19.25	$19.20
Purchase #2	$152.34	12.867%	$171.9416	$171.94	$171.95	$171.90
Purchase #3	$163.74	4.600%	$171.272	$171.27	$171.25	$171.30
Purchase #4	$204.61	6.497%	$217.9035	$217.90	$217.90	$217.90
Purchase #5	$75.30	10.297%	$83.0536	$83.05	$83.05	$83.10
Purchase #6	$150.91	3.571%	$156.299	$156.30	$156.30	$156.30
Purchase #7	$138.43	3.116%	$142.7435	$142.74	$142.75	$142.70
7 purchase totals =	$903.61		$962.4474	$962.43	$962.45	$962.40