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	$234.78	8.201%	$254.0343	$254.03	$254.05	$254.00
Purchase #2	$191.31	8.473%	$207.5197	$207.52	$207.50	$207.50
Purchase #3	$84.45	10.159%	$93.0293	$93.03	$93.05	$93.00
Purchase #4	$184.41	6.607%	$196.594	$196.59	$196.60	$196.60
Purchase #5	$66.83	7.732%	$71.9973	$72.00	$72.00	$72.00
Purchase #6	$72.63	7.409%	$78.0112	$78.01	$78.00	$78.00
Purchase #7	$157.38	10.739%	$174.281	$174.28	$174.30	$174.30
7 purchase totals =	$991.79		$1,075.4668	$1,075.46	$1,075.50	$1,075.40