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	$22.99	11.264%	$25.5796	$25.58	$25.60	$25.60
Purchase #2	$28.96	11.868%	$32.397	$32.40	$32.40	$32.40
Purchase #3	$191.56	3.529%	$198.3202	$198.32	$198.30	$198.30
Purchase #4	$193.46	7.405%	$207.7857	$207.79	$207.80	$207.80
Purchase #5	$181.62	4.676%	$190.1126	$190.11	$190.10	$190.10
Purchase #6	$90.40	11.234%	$100.5555	$100.56	$100.55	$100.60
Purchase #7	$82.53	10.683%	$91.3467	$91.35	$91.35	$91.30
7 purchase totals =	$791.52		$846.0973	$846.11	$846.10	$846.10