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	$107.40	8.122%	$116.123	$116.12	$116.10	$116.10
Purchase #2	$211.85	4.102%	$220.5401	$220.54	$220.55	$220.50
Purchase #3	$98.73	12.590%	$111.1601	$111.16	$111.15	$111.20
Purchase #4	$81.94	13.871%	$93.3059	$93.31	$93.30	$93.30
Purchase #5	$45.82	13.814%	$52.1496	$52.15	$52.15	$52.10
Purchase #6	$210.80	13.854%	$240.0042	$240.00	$240.00	$240.00
Purchase #7	$137.32	4.114%	$142.9693	$142.97	$142.95	$143.00
7 purchase totals =	$893.86		$976.2522	$976.25	$976.20	$976.20