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	$188.86	9.648%	$207.0812	$207.08	$207.10	$207.10
Purchase #2	$190.85	12.860%	$215.3933	$215.39	$215.40	$215.40
Purchase #3	$173.52	7.327%	$186.2338	$186.23	$186.25	$186.20
Purchase #4	$123.54	11.411%	$137.6371	$137.64	$137.65	$137.60
Purchase #5	$99.35	5.519%	$104.8331	$104.83	$104.85	$104.80
Purchase #6	$166.47	9.335%	$182.01	$182.01	$182.00	$182.00
Purchase #7	$82.73	8.348%	$89.6363	$89.64	$89.65	$89.60
7 purchase totals =	$1,025.32		$1,122.8248	$1,122.82	$1,122.90	$1,122.70