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	$220.98	7.300%	$237.1115	$237.11	$237.10	$237.10
Purchase #2	$137.84	13.356%	$156.2499	$156.25	$156.25	$156.20
Purchase #3	$190.97	4.371%	$199.3173	$199.32	$199.30	$199.30
Purchase #4	$201.46	10.803%	$223.2237	$223.22	$223.20	$223.20
Purchase #5	$73.86	11.268%	$82.1825	$82.18	$82.20	$82.20
Purchase #6	$123.78	3.192%	$127.7311	$127.73	$127.75	$127.70
Purchase #7	$155.25	12.162%	$174.1315	$174.13	$174.15	$174.10
7 purchase totals =	$1,104.14		$1,199.9475	$1,199.94	$1,199.95	$1,199.80