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	$223.39	10.615%	$247.1028	$247.10	$247.10	$247.10
Purchase #2	$138.93	11.112%	$154.3679	$154.37	$154.35	$154.40
Purchase #3	$130.89	7.831%	$141.14	$141.14	$141.15	$141.10
Purchase #4	$157.91	4.555%	$165.1028	$165.10	$165.10	$165.10
Purchase #5	$185.86	4.816%	$194.811	$194.81	$194.80	$194.80
Purchase #6	$31.55	11.120%	$35.0584	$35.06	$35.05	$35.10
Purchase #7	$102.39	3.416%	$105.8876	$105.89	$105.90	$105.90
7 purchase totals =	$970.92		$1,043.4705	$1,043.47	$1,043.45	$1,043.50