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	$18.27	4.312%	$19.0578	$19.06	$19.05	$19.10
Purchase #2	$160.38	3.258%	$165.6052	$165.61	$165.60	$165.60
Purchase #3	$11.76	13.370%	$13.3323	$13.33	$13.35	$13.30
Purchase #4	$96.69	3.519%	$100.0925	$100.09	$100.10	$100.10
Purchase #5	$139.28	13.132%	$157.5702	$157.57	$157.55	$157.60
Purchase #6	$141.42	10.676%	$156.518	$156.52	$156.50	$156.50
Purchase #7	$39.49	9.481%	$43.234	$43.23	$43.25	$43.20
7 purchase totals =	$607.29		$655.4100	$655.41	$655.40	$655.40