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	$207.41	7.873%	$223.7394	$223.74	$223.75	$223.70
Purchase #2	$72.98	12.812%	$82.3302	$82.33	$82.35	$82.30
Purchase #3	$155.68	9.136%	$169.9029	$169.90	$169.90	$169.90
Purchase #4	$97.86	10.601%	$108.2341	$108.23	$108.25	$108.20
Purchase #5	$67.44	6.358%	$71.7278	$71.73	$71.75	$71.70
Purchase #6	$231.68	3.158%	$238.9965	$239.00	$239.00	$239.00
Purchase #7	$153.78	11.596%	$171.6123	$171.61	$171.60	$171.60
7 purchase totals =	$986.83		$1,066.5432	$1,066.54	$1,066.60	$1,066.40