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	$182.98	5.111%	$192.3321	$192.33	$192.35	$192.30
Purchase #2	$105.49	10.279%	$116.3333	$116.33	$116.35	$116.30
Purchase #3	$167.82	6.445%	$178.636	$178.64	$178.65	$178.60
Purchase #4	$102.35	13.495%	$116.1621	$116.16	$116.15	$116.20
Purchase #5	$215.92	13.825%	$245.7709	$245.77	$245.75	$245.80
Purchase #6	$14.39	4.865%	$15.0901	$15.09	$15.10	$15.10
Purchase #7	$96.59	3.508%	$99.9784	$99.98	$100.00	$100.00
7 purchase totals =	$885.54		$964.3029	$964.30	$964.35	$964.30