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	$121.44	9.668%	$133.1808	$133.18	$133.20	$133.20
Purchase #2	$144.82	4.477%	$151.3036	$151.30	$151.30	$151.30
Purchase #3	$163.82	10.537%	$181.0817	$181.08	$181.10	$181.10
Purchase #4	$54.60	13.779%	$62.1233	$62.12	$62.10	$62.10
Purchase #5	$171.54	13.720%	$195.0753	$195.08	$195.10	$195.10
Purchase #6	$204.78	12.855%	$231.1045	$231.10	$231.10	$231.10
Purchase #7	$80.32	11.112%	$89.2452	$89.25	$89.25	$89.20
7 purchase totals =	$941.32		$1,043.1144	$1,043.11	$1,043.15	$1,043.10