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	$112.92	12.603%	$127.1513	$127.15	$127.15	$127.20
Purchase #2	$191.98	6.408%	$204.2821	$204.28	$204.30	$204.30
Purchase #3	$173.96	5.328%	$183.2286	$183.23	$183.25	$183.20
Purchase #4	$242.28	8.694%	$263.3438	$263.34	$263.35	$263.30
Purchase #5	$210.35	8.320%	$227.8511	$227.85	$227.85	$227.90
Purchase #6	$165.95	4.614%	$173.6069	$173.61	$173.60	$173.60
Purchase #7	$202.83	9.629%	$222.3605	$222.36	$222.35	$222.40
7 purchase totals =	$1,300.27		$1,401.8243	$1,401.82	$1,401.85	$1,401.90