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	$96.95	10.827%	$107.4468	$107.45	$107.45	$107.40
Purchase #2	$139.91	11.327%	$155.7576	$155.76	$155.75	$155.80
Purchase #3	$209.37	5.243%	$220.3473	$220.35	$220.35	$220.30
Purchase #4	$92.75	4.130%	$96.5806	$96.58	$96.60	$96.60
Purchase #5	$77.90	5.336%	$82.0567	$82.06	$82.05	$82.10
Purchase #6	$72.31	13.838%	$82.3163	$82.32	$82.30	$82.30
Purchase #7	$226.58	11.824%	$253.3708	$253.37	$253.35	$253.40
7 purchase totals =	$915.77		$997.8761	$997.89	$997.85	$997.90