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	$185.95	11.485%	$207.3064	$207.31	$207.30	$207.30
Purchase #2	$121.76	4.389%	$127.104	$127.10	$127.10	$127.10
Purchase #3	$50.81	4.647%	$53.1711	$53.17	$53.15	$53.20
Purchase #4	$84.36	6.405%	$89.7633	$89.76	$89.75	$89.80
Purchase #5	$13.48	7.605%	$14.5052	$14.51	$14.50	$14.50
Purchase #6	$17.97	9.617%	$19.6982	$19.70	$19.70	$19.70
Purchase #7	$84.44	6.432%	$89.8712	$89.87	$89.85	$89.90
7 purchase totals =	$558.77		$601.4194	$601.42	$601.35	$601.50