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	$99.26	4.697%	$103.9222	$103.92	$103.90	$103.90
Purchase #2	$79.73	8.774%	$86.7255	$86.73	$86.75	$86.70
Purchase #3	$176.32	8.412%	$191.152	$191.15	$191.15	$191.20
Purchase #4	$80.43	12.321%	$90.3398	$90.34	$90.35	$90.30
Purchase #5	$76.92	10.518%	$85.0104	$85.01	$85.00	$85.00
Purchase #6	$187.92	9.281%	$205.3609	$205.36	$205.35	$205.40
Purchase #7	$244.87	4.402%	$255.6492	$255.65	$255.65	$255.60
7 purchase totals =	$945.45		$1,018.1600	$1,018.16	$1,018.15	$1,018.10