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	$139.30	9.653%	$152.7466	$152.75	$152.75	$152.70
Purchase #2	$45.89	8.206%	$49.6557	$49.66	$49.65	$49.70
Purchase #3	$103.69	5.367%	$109.255	$109.26	$109.25	$109.30
Purchase #4	$84.46	6.865%	$90.2582	$90.26	$90.25	$90.30
Purchase #5	$215.30	10.251%	$237.3704	$237.37	$237.35	$237.40
Purchase #6	$205.32	3.208%	$211.9067	$211.91	$211.90	$211.90
Purchase #7	$98.68	11.238%	$109.7697	$109.77	$109.75	$109.80
7 purchase totals =	$892.64		$960.9623	$960.98	$960.90	$961.10