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	$242.81	9.284%	$265.3525	$265.35	$265.35	$265.40
Purchase #2	$94.58	5.108%	$99.4111	$99.41	$99.40	$99.40
Purchase #3	$196.59	12.464%	$221.093	$221.09	$221.10	$221.10
Purchase #4	$89.53	5.705%	$94.6377	$94.64	$94.65	$94.60
Purchase #5	$165.98	12.801%	$187.2271	$187.23	$187.25	$187.20
Purchase #6	$185.40	6.128%	$196.7613	$196.76	$196.75	$196.80
Purchase #7	$149.40	12.393%	$167.9151	$167.92	$167.90	$167.90
7 purchase totals =	$1,124.29		$1,232.3978	$1,232.40	$1,232.40	$1,232.40