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	$239.41	4.496%	$250.1739	$250.17	$250.15	$250.20
Purchase #2	$5.37	10.337%	$5.9251	$5.93	$5.95	$5.90
Purchase #3	$165.40	3.829%	$171.7332	$171.73	$171.75	$171.70
Purchase #4	$200.51	11.250%	$223.0674	$223.07	$223.05	$223.10
Purchase #5	$33.67	5.548%	$35.538	$35.54	$35.55	$35.50
Purchase #6	$208.32	13.696%	$236.8515	$236.85	$236.85	$236.90
Purchase #7	$68.45	4.208%	$71.3304	$71.33	$71.35	$71.30
7 purchase totals =	$921.13		$994.6195	$994.62	$994.65	$994.60