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	$105.81	12.864%	$119.4214	$119.42	$119.40	$119.40
Purchase #2	$66.76	6.827%	$71.3177	$71.32	$71.30	$71.30
Purchase #3	$151.31	6.322%	$160.8758	$160.88	$160.90	$160.90
Purchase #4	$174.42	12.403%	$196.0533	$196.05	$196.05	$196.10
Purchase #5	$227.64	9.376%	$248.9835	$248.98	$249.00	$249.00
Purchase #6	$48.43	5.192%	$50.9445	$50.94	$50.95	$50.90
Purchase #7	$106.30	11.155%	$118.1578	$118.16	$118.15	$118.20
7 purchase totals =	$880.67		$965.7540	$965.75	$965.75	$965.80