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	$104.31	7.377%	$112.0049	$112.00	$112.00	$112.00
Purchase #2	$71.42	9.640%	$78.3049	$78.30	$78.30	$78.30
Purchase #3	$19.55	6.783%	$20.8761	$20.88	$20.90	$20.90
Purchase #4	$126.98	5.306%	$133.7176	$133.72	$133.70	$133.70
Purchase #5	$147.86	5.196%	$155.5428	$155.54	$155.55	$155.50
Purchase #6	$229.45	7.419%	$246.4729	$246.47	$246.45	$246.50
Purchase #7	$163.62	9.314%	$178.8596	$178.86	$178.85	$178.90
7 purchase totals =	$863.19		$925.7788	$925.77	$925.75	$925.80