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	$66.76	4.293%	$69.626	$69.63	$69.65	$69.60
Purchase #2	$54.31	9.596%	$59.5216	$59.52	$59.50	$59.50
Purchase #3	$110.47	4.231%	$115.144	$115.14	$115.15	$115.10
Purchase #4	$88.50	13.673%	$100.6006	$100.60	$100.60	$100.60
Purchase #5	$44.35	6.868%	$47.396	$47.40	$47.40	$47.40
Purchase #6	$143.84	11.758%	$160.7527	$160.75	$160.75	$160.80
Purchase #7	$133.56	6.847%	$142.7049	$142.70	$142.70	$142.70
7 purchase totals =	$641.79		$695.7458	$695.74	$695.75	$695.70