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	$196.54	6.504%	$209.323	$209.32	$209.30	$209.30
Purchase #2	$80.36	6.188%	$85.3327	$85.33	$85.35	$85.30
Purchase #3	$172.91	3.447%	$178.8702	$178.87	$178.85	$178.90
Purchase #4	$204.74	10.835%	$226.9236	$226.92	$226.90	$226.90
Purchase #5	$45.62	12.783%	$51.4516	$51.45	$51.45	$51.50
Purchase #6	$237.41	5.525%	$250.5269	$250.53	$250.55	$250.50
Purchase #7	$210.96	13.236%	$238.8827	$238.88	$238.90	$238.90
7 purchase totals =	$1,148.54		$1,241.3107	$1,241.30	$1,241.30	$1,241.30