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	$6.52	8.142%	$7.0509	$7.05	$7.05	$7.10
Purchase #2	$76.33	8.472%	$82.7967	$82.80	$82.80	$82.80
Purchase #3	$181.39	3.813%	$188.3064	$188.31	$188.30	$188.30
Purchase #4	$119.27	6.727%	$127.2933	$127.29	$127.30	$127.30
Purchase #5	$71.43	5.659%	$75.4722	$75.47	$75.45	$75.50
Purchase #6	$197.34	7.638%	$212.4128	$212.41	$212.40	$212.40
Purchase #7	$151.82	5.685%	$160.451	$160.45	$160.45	$160.50
7 purchase totals =	$804.10		$853.7833	$853.78	$853.75	$853.90