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	$184.94	8.418%	$200.5082	$200.51	$200.50	$200.50
Purchase #2	$191.70	12.348%	$215.3711	$215.37	$215.35	$215.40
Purchase #3	$144.67	9.297%	$158.12	$158.12	$158.10	$158.10
Purchase #4	$177.46	4.871%	$186.1041	$186.10	$186.10	$186.10
Purchase #5	$115.94	11.191%	$128.9148	$128.91	$128.90	$128.90
Purchase #6	$160.88	4.655%	$168.369	$168.37	$168.35	$168.40
Purchase #7	$122.70	9.313%	$134.1271	$134.13	$134.15	$134.10
7 purchase totals =	$1,098.29		$1,191.5143	$1,191.51	$1,191.45	$1,191.50