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	$177.42	4.326%	$185.0952	$185.10	$185.10	$185.10
Purchase #2	$75.40	12.818%	$85.0648	$85.06	$85.05	$85.10
Purchase #3	$10.46	3.279%	$10.803	$10.80	$10.80	$10.80
Purchase #4	$120.27	9.780%	$132.0324	$132.03	$132.05	$132.00
Purchase #5	$39.61	10.563%	$43.794	$43.79	$43.80	$43.80
Purchase #6	$170.52	12.545%	$191.9117	$191.91	$191.90	$191.90
Purchase #7	$215.75	6.191%	$229.1071	$229.11	$229.10	$229.10
7 purchase totals =	$809.43		$877.8082	$877.80	$877.80	$877.80