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	$138.63	9.196%	$151.3784	$151.38	$151.40	$151.40
Purchase #2	$84.79	5.235%	$89.2288	$89.23	$89.25	$89.20
Purchase #3	$239.32	11.343%	$266.4661	$266.47	$266.45	$266.50
Purchase #4	$214.27	7.128%	$229.5432	$229.54	$229.55	$229.50
Purchase #5	$147.98	8.416%	$160.434	$160.43	$160.45	$160.40
Purchase #6	$104.92	9.497%	$114.8843	$114.88	$114.90	$114.90
Purchase #7	$190.45	5.132%	$200.2239	$200.22	$200.20	$200.20
7 purchase totals =	$1,120.36		$1,212.1587	$1,212.15	$1,212.20	$1,212.10