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	$197.43	13.119%	$223.3308	$223.33	$223.35	$223.30
Purchase #2	$114.90	7.450%	$123.4601	$123.46	$123.45	$123.50
Purchase #3	$240.95	6.562%	$256.7611	$256.76	$256.75	$256.80
Purchase #4	$29.67	4.160%	$30.9043	$30.90	$30.90	$30.90
Purchase #5	$225.33	13.360%	$255.4341	$255.43	$255.45	$255.40
Purchase #6	$163.88	6.676%	$174.8206	$174.82	$174.80	$174.80
Purchase #7	$216.46	4.653%	$226.5319	$226.53	$226.55	$226.50
7 purchase totals =	$1,188.62		$1,291.2429	$1,291.23	$1,291.25	$1,291.20