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	$212.31	13.524%	$241.0228	$241.02	$241.00	$241.00
Purchase #2	$41.76	3.607%	$43.2663	$43.27	$43.25	$43.30
Purchase #3	$99.92	11.492%	$111.4028	$111.40	$111.40	$111.40
Purchase #4	$248.26	9.126%	$270.9162	$270.92	$270.90	$270.90
Purchase #5	$236.98	8.258%	$256.5498	$256.55	$256.55	$256.50
Purchase #6	$221.47	3.580%	$229.3986	$229.40	$229.40	$229.40
Purchase #7	$141.42	13.332%	$160.2741	$160.27	$160.25	$160.30
7 purchase totals =	$1,202.12		$1,312.8306	$1,312.83	$1,312.75	$1,312.80