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	$38.97	10.251%	$42.9648	$42.96	$42.95	$43.00
Purchase #2	$198.66	4.406%	$207.413	$207.41	$207.40	$207.40
Purchase #3	$49.80	7.432%	$53.5011	$53.50	$53.50	$53.50
Purchase #4	$100.67	10.817%	$111.5595	$111.56	$111.55	$111.60
Purchase #5	$9.88	12.598%	$11.1247	$11.12	$11.10	$11.10
Purchase #6	$195.90	5.741%	$207.1466	$207.15	$207.15	$207.10
Purchase #7	$57.44	3.162%	$59.2563	$59.26	$59.25	$59.30
7 purchase totals =	$651.32		$692.9660	$692.96	$692.90	$693.00