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	$119.97	6.543%	$127.8196	$127.82	$127.80	$127.80
Purchase #2	$119.43	10.325%	$131.7611	$131.76	$131.75	$131.80
Purchase #3	$173.25	9.422%	$189.5736	$189.57	$189.55	$189.60
Purchase #4	$214.32	6.803%	$228.9002	$228.90	$228.90	$228.90
Purchase #5	$49.71	7.171%	$53.2747	$53.27	$53.25	$53.30
Purchase #6	$61.49	9.492%	$67.3266	$67.33	$67.35	$67.30
Purchase #7	$219.91	5.182%	$231.3057	$231.31	$231.30	$231.30
7 purchase totals =	$958.08		$1,029.9615	$1,029.96	$1,029.90	$1,030.00