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	$147.25	11.501%	$164.1852	$164.19	$164.20	$164.20
Purchase #2	$206.25	4.488%	$215.5065	$215.51	$215.50	$215.50
Purchase #3	$145.91	5.594%	$154.0722	$154.07	$154.05	$154.10
Purchase #4	$23.86	6.568%	$25.4271	$25.43	$25.45	$25.40
Purchase #5	$143.30	13.272%	$162.3188	$162.32	$162.30	$162.30
Purchase #6	$160.43	6.670%	$171.1307	$171.13	$171.15	$171.10
Purchase #7	$206.91	13.462%	$234.7642	$234.76	$234.75	$234.80
7 purchase totals =	$1,033.91		$1,127.4047	$1,127.41	$1,127.40	$1,127.40