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	$92.52	7.113%	$99.1009	$99.10	$99.10	$99.10
Purchase #2	$71.82	9.232%	$78.4504	$78.45	$78.45	$78.50
Purchase #3	$248.85	13.645%	$282.8056	$282.81	$282.80	$282.80
Purchase #4	$29.62	5.682%	$31.303	$31.30	$31.30	$31.30
Purchase #5	$195.93	9.258%	$214.0692	$214.07	$214.05	$214.10
Purchase #6	$248.70	4.589%	$260.1128	$260.11	$260.10	$260.10
Purchase #7	$178.96	4.301%	$186.6571	$186.66	$186.65	$186.70
7 purchase totals =	$1,066.40		$1,152.4990	$1,152.50	$1,152.45	$1,152.60