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	$187.54	4.788%	$196.5194	$196.52	$196.50	$196.50
Purchase #2	$101.68	8.256%	$110.0747	$110.07	$110.05	$110.10
Purchase #3	$190.98	4.783%	$200.1146	$200.11	$200.10	$200.10
Purchase #4	$244.48	3.488%	$253.0075	$253.01	$253.00	$253.00
Purchase #5	$185.54	12.831%	$209.3466	$209.35	$209.35	$209.30
Purchase #6	$64.97	3.563%	$67.2849	$67.28	$67.30	$67.30
Purchase #7	$39.63	5.212%	$41.6955	$41.70	$41.70	$41.70
7 purchase totals =	$1,014.82		$1,078.0432	$1,078.04	$1,078.00	$1,078.00