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	$166.82	4.354%	$174.0833	$174.08	$174.10	$174.10
Purchase #2	$113.68	4.809%	$119.1469	$119.15	$119.15	$119.10
Purchase #3	$126.58	12.590%	$142.5164	$142.52	$142.50	$142.50
Purchase #4	$23.66	8.211%	$25.6027	$25.60	$25.60	$25.60
Purchase #5	$93.88	6.419%	$99.9062	$99.91	$99.90	$99.90
Purchase #6	$219.80	9.718%	$241.1602	$241.16	$241.15	$241.20
Purchase #7	$156.27	12.518%	$175.8319	$175.83	$175.85	$175.80
7 purchase totals =	$900.69		$978.2476	$978.25	$978.25	$978.20