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	$201.81	10.566%	$223.1332	$223.13	$223.15	$223.10
Purchase #2	$72.78	13.106%	$82.3185	$82.32	$82.30	$82.30
Purchase #3	$158.65	8.240%	$171.7228	$171.72	$171.70	$171.70
Purchase #4	$16.96	4.270%	$17.6842	$17.68	$17.70	$17.70
Purchase #5	$224.76	5.779%	$237.7489	$237.75	$237.75	$237.70
Purchase #6	$227.82	9.872%	$250.3104	$250.31	$250.30	$250.30
Purchase #7	$199.28	11.832%	$222.8588	$222.86	$222.85	$222.90
7 purchase totals =	$1,102.06		$1,205.7768	$1,205.77	$1,205.75	$1,205.70