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	$169.41	5.650%	$178.9817	$178.98	$179.00	$179.00
Purchase #2	$55.27	13.727%	$62.8569	$62.86	$62.85	$62.90
Purchase #3	$181.33	8.384%	$196.5327	$196.53	$196.55	$196.50
Purchase #4	$148.81	4.208%	$155.0719	$155.07	$155.05	$155.10
Purchase #5	$18.98	8.740%	$20.6389	$20.64	$20.65	$20.60
Purchase #6	$223.94	9.650%	$245.5502	$245.55	$245.55	$245.60
Purchase #7	$212.95	11.624%	$237.7033	$237.70	$237.70	$237.70
7 purchase totals =	$1,010.69		$1,097.3356	$1,097.33	$1,097.35	$1,097.40