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	$25.68	5.615%	$27.1219	$27.12	$27.10	$27.10
Purchase #2	$96.39	3.126%	$99.4032	$99.40	$99.40	$99.40
Purchase #3	$244.68	4.288%	$255.1719	$255.17	$255.15	$255.20
Purchase #4	$219.37	10.463%	$242.3227	$242.32	$242.30	$242.30
Purchase #5	$117.80	8.280%	$127.5538	$127.55	$127.55	$127.60
Purchase #6	$6.57	10.801%	$7.2796	$7.28	$7.30	$7.30
Purchase #7	$117.80	4.267%	$122.8265	$122.83	$122.85	$122.80
7 purchase totals =	$828.29		$881.6796	$881.67	$881.65	$881.70